EC6802 WIRELESS NETWORKS.

EC WIRELESS NETWORKS

OBJECTIVES To study about Wireless networks, protocol stack and standards. To study about fundamentals of 3G Services, its protocols and applications. To study about evolution of 4G Networks, its architecture and applications.

UNIT I WIRELESS LAN Introduction-WLAN technologies: Infrared, UHF narrowband, spread spectrum -IEEE802.11: System architecture, protocol architecture, physical layer, MAC layer, b, a – Hiper LAN: WATM, BRAN, HiperLAN2 – Bluetooth: Architecture, Radio Layer, Baseband layer, Link manager Protocol, security - IEEE WIMAX: Physical layer, MAC, Spectrum allocation for WIMAX UNIT II MOBILE NETWORK LAYER Introduction - Mobile IP: IP packet delivery, Agent discovery, tunneling and encapsulation, IPV6-Network layer in the internet- Mobile IP session initiation protocol - mobile ad-hoc network: Routing, Destination Sequence distance vector, Dynamic source routing UNIT III MOBILE TRANSPORT LAYER TCP enhancements for wireless protocols - Traditional TCP: Congestion control, fast retransmit/fast recovery, Implications of mobility - Classical TCP improvements: Indirect TCP, Snooping TCP, Mobile TCP, Time out freezing, Selective retransmission, Transaction oriented TCP - TCP over 3G wireless networks.

UNIT IV WIRELESS WIDE AREA NETWORK Overview of UTMS Terrestrial Radio access network-UMTS Core network Architecture: 3G-MSC, 3G-SGSN, 3G- GGSN, SMS-GMSC/SMS-IWMSC, Firewall, DNS/DHCP-High speed Downlink packet access (HSDPA)- LTE network architecture and protocol. UNIT V 4G NETWORKS Introduction – 4G vision – 4G features and challenges - Applications of 4G – 4G Technologies: Multicarrier Modulation, Smart antenna techniques, OFDM-MIMO systems, Adaptive Modulation and coding with time slot scheduler, Cognitive Radio.

OUTCOMES: Upon completion of the course, the students will be able to
Conversant with the latest 3G/4G and WiMAX networks and its architecture. Design and implement wireless network environment for any application using latest wireless protocols and standards. Implement different type of applications for smart phones and mobile devices with latest network strategies.

TEXT BOOKS: 1. Jochen Schiller, ”Mobile Communications”, Second Edition, Pearson Education 2012.(Unit I,II,III) 2. Vijay Garg, “Wireless Communications and networking”, First Edition, Elsevier 2007.(Unit IV,V) REFERENCES: 1. Erik Dahlman, Stefan Parkvall, Johan Skold and Per Beming, "3G Evolution HSPA and LTE for Mobile Broadband”, Second Edition, Academic Press, 2008. 2. Anurag Kumar, D.Manjunath, Joy kuri, “Wireless Networking”, First Edition, Elsevier 2011. 3. Simon Haykin , Michael Moher, David Koilpillai, “Modern Wireless Communications”, First Edition, Pearson Education 2013

UNIT I WIRELESS LAN

OVERVIEW: Introduction WLAN technologies: Infrared, UHF narrowband, spread spectrum - IEEE802.11: System architecture, protocol architecture, physical layer, MAC layer, b, a Hiper LAN: WATM, BRAN, HiperLAN2 Bluetooth: Architecture, Radio Layer, Baseband layer, Link manager Protocol, security - IEEE802.16 WIMAX: Physical layer, MAC, Spectrum allocation for WIMAX

INTRODUCTION Wireless means transmitting signals using radio waves as the medium instead of wires. Wireless technologies are used for tasks as simple as switching off the television or as complex as supplying the sales force with information from an automated enterprise application while in the field. Now cordless keyboards, mice and cellular phones have become part of our daily life.

Some of the inherent characteristics of wireless communications systems which make it attractive for users, are given below − Mobility − A wireless communications system allows users to access information beyond their desk and conduct business from anywhere without having a wire connectivity. Reachability − Wireless communication systems enable people to be stay connected and be reachable, regardless of the location they are operating from. Simplicity − Wireless communication system are easy and fast to deploy in comparison of cabled network. Initial setup cost could be a bit high but other advantages overcome that high cost.

Maintainability − In a wireless system, you do not have to spend too much cost and time to maintain the network setup. Roaming Services − Using a wireless network system, you can provide service any where any time including train, buses, aero planes etc. New Services − Wireless communication systems provide various smart services like SMS and MMS.

WIRELESS NETWORK TOPOLOGIES
There are basically three ways to set up a wireless network POINT-TO-POINT BRIDGE As you know, a bridge is used to connect two networks. A point-to-point bridge interconnects two buildings having different networks. For example, a wireless LAN bridge can interface with an Ethernet network directly to a particular access point.

POINT-TO-MULTIPOINT BRIDGE
This topology is used to connect three or more LANs that may be located on different floors in a building or across buildings

MESH OR AD HOC NETWORK This network is an independent local area network that is not connected to a wired infrastructure and in which all stations are connected directly to one another

WIRELESS TECHNOLOGIES
Wireless technologies can be classified in different ways depending on their range. Each wireless technology is designed to serve a specific usage segment. The requirements for each usage segment are based on a variety of variables, including Bandwidth needs, Distance needs and Power. Wireless Wide Area Network (WWAN) This network enables you to access the Internet via a wireless wide area network (WWAN) access card and a PDA or laptop. These networks provide a very fast data speed compared with the data rates of mobile telecommunications technology, and their range is also extensive. Cellular and mobile networks based on CDMA and GSM are good examples of WWAN. Wireless Personal Area Network (WPAN) These networks are very similar to WWAN except their range is very limited.

WIRELESS METROPOLITAN AREA NETWORK (WMAN)
WIRELESS LOCAL AREA NETWORK (WLAN) This network enables you to access the Internet in localized hotspots via a wireless local area network (WLAN) access card and a PDA or laptop. It is a type of local area network that uses high-frequency radio waves rather than wires to communicate between nodes. These networks provide a very fast data speed compared with the data rates of mobile telecommunications technology, and their range is very limited. Wi-Fi is the most widespread and popular example of WLAN technology. WIRELESS METROPOLITAN AREA NETWORK (WMAN) This network enables you to access the Internet and multimedia streaming services via a wireless region area network (WRAN). These networks provide a very fast data speed compared with the data rates of mobile telecommunication technology as well as other wireless network, and their range is also extensive.

ISSUES WITH WIRELESS NETWORKS
There are following three major issues with Wireless Networks. Quality of Service (QoS): One of the primary concerns about wireless data delivery is that, unlike the Internet through wired services, QoS is inadequate. Lost packets and atmospheric interference are recurring problems of the wireless protocols. WLANs typically offer lower quality than their wired counterparts. The main reasons for this are the lower bandwidth due to limitations in radio transmission (e.g., only 1–10 Mbit/s user data rate instead of 100–1,000 Mbit/s) Security Risk: This is another major issue with a data transfer over a wireless network. Basic network security mechanisms like the service set identifier (SSID) and Wireless Equivalency Privacy (WEP); these measures may be adequate for residences and small businesses, but they are inadequate for the entities that require stronger security.

Reachable Range: Normally, wireless network offers a range of about 100 meters or less. Range is a function of antenna design and power. Now a days the range of wireless is extended to tens of miles so this should not be an issue any more. Proprietary solutions: Due to slow standardization procedures, many companies have come up with proprietary solutions offering standardized functionality plus many enhanced features. At least most components today adhere to the basic standards IEEE b or (newer) a

Design goals have to be taken into account for WLANs to ensure their commercial success
Global operation: WLAN products should sell in all countries so, national and international frequency regulations have to be considered. Low power: Devices communicating via a WLAN are typically also wireless devices running on battery power. The LAN design should take this into account and implement special power-saving modes and power management functions. License-free operation: LAN operators do not want to apply for a special license to be able to use the product. The equipment must operate in a license-free band, such as the 2.4 GHz ISM band.

Robust transmission technology: Compared to their wired counterparts, WLANs operate under difficult conditions. If they use radio transmission, many other electrical devices can interfere with them (vacuum cleaners, hairdryers, train engines etc.). Easy to use: In contrast to huge and complex wireless WANs, wireless LANs are made for simple use. They should not require complex management, but rather work on a plug-and-play basis. Protection of investment: A lot of money has already been invested into wired LANs. The new WLANs should protect this investment by being interoperable with the existing networks. This means that simple bridging between the different LANs should be enough to interoperate, i.e., the wireless LANs should support the same data types and services that standard LANs support. Transparency for applications: Existing applications should continue to run over WLANs

INFRASTRUCTURE AND AD-HOC NETWORKS
Many WLANs of today need an infrastructure network. Infrastructure networks not only provide access to other networks, but also include forwarding functions, medium access control etc. In these infrastructure-based wireless networks, communication typically takes place only between the wireless nodes and the access point , but not directly between the wireless nodes.

Infrastructure-based wireless networks

The access point does not just control medium access, but also acts as a bridge to other wireless or wired networks. Several wireless networks may form one logical wireless network, so the access points together with the fixed network in between can connect several wireless networks to form a larger network beyond actual radio coverage. Design of infrastructure-based wireless networks is simpler. This structure is reminiscent of switched Ethernet or other star-based networks, where a central element (e.g., a switch) controls network flow. Typical cellular phone networks are infrastructure-based networks for a wide area . Also satellite-based cellular phones have an infrastructure – the satellites

ad-hoc wireless networks
Ad-hoc wireless networks, however, do not need any infrastructure to work. Each node can communicate directly with other nodes, so no access point controlling medium access is necessary. Nodes within an ad-hoc network can only communicate if they can reach each other physically, i.e., if they are within each others radio range or if other nodes can forward the message. In ad-hoc networks, the complexity of each node is higher because every node has to implement medium access mechanisms ad-hoc wireless networks

EXAMPLE: IEEE and HiperLAN2 are typically infrastructure-based networks, which additionally support ad-hoc networking. Bluetooth is a typical wireless ad-hoc network.

WLAN TECHNOLOGIES: INFRARED UHF(Narrow band) SPREAD SPECTRUM

1. Infrared Technology: Infrared is an invisible band of radiation that exists at lower end of visible electromagnetic spectrum. There are two types of infrared WLAN solutions: Direct beam (or line-of-sight) Diffused beam (uses reflected rays) Direct beam WLANs offer faster data rates while diffused beam technology achieves lower data rates in 1-2 Mbps range. The advantage of using this technology is that there are no government regulations on its use and also it is immune to EM and RF interference. The disadvantage is that it is a short range technology (30-50 ft radius under ideal conditions).Also, it requires line-of-sight. The signal gets affected by solid objects like doors, walls, etc. The signal is also affected by fog, dirt, ice, snow.

2. UHF Narrowband technology:
The frequency range is 430 to 470 MHZ and rarely segments in 800 MHZ range. The portion MHZ is unlicensed while MHZ band is licensed. The term narrow band is used because RF signal is sent in a very narrow band width, typically 12.5 KHz or 25 KHz. There are two systems: Synthesized and Un-synthesized system uses crystal controlled frequency operation. There can be frequency drift problem in crystal. The synthesized uses single, standard crystal. Multiple frequencies are achieved using dividing the crystal frequency and then multiplying it to desired channel frequency. The advantage of this technology is that it has longest range and its low cost for large sites. The disadvantages of this include the need of license, no multivendor inter operability and interference potential.

3.Spread Spectrum Technology:
In this technique, the entire allotted bandwidth is shared instead of dividing it into discrete private parts. The spread spectrum spreads the transmission power over entire usable spectrum. Thus, though bandwidth efficiency decreases; reliability, integrity and security increase. In commercial applications, spread spectrum techniques currently offer data rates up to 2Mbps. Two modulation schemes are used to encode spread spectrum signals : frequency hopping spread spectrum (FHSS) and direct sequence spread spectrum (DSSS) FHSS uses a narrowband carrier that changes frequency in a pattern known to both transmitter and receiver. To some other receiver, FHSS appears to be a short- duration impulse noise. Thus, the data security increases. Similarly, DSSS generates redundant bit pattern for every bit to be transmitted, known as spreading code, known only to transmitter and receiver. To some other receiver, DSSS appears as low-power, wideband noise and is rejected.

IEEE 802.11 Wi-Fi Wireless LAN Media Access Control and Physical Layer specification a,b,g,etc. are amendments to the original standard. Products that implement standards must pass tests and are referred to as "Wi-Fi certified." Additional features of the WLAN should include the support of power management to save battery power, the handling of hidden nodes, and the ability to operate worldwide. The 2.4 GHz ISM band, which is available in most countries around the world, was chosen for the original standard.

IEEE : System architecture Protocol architecture Physical layer MAC layer 802.11b 802.11a

Freie Universität Berlin Institut of Computer Science
Mobile Communications 2002 System architecture Wireless networks can exhibit two different basic system architectures infrastructure-based or ad-hoc. Station (STA) terminal with access mechanisms to the wireless medium and radio contact to the access point Basic Service Set (BSS) group of stations using the same radio frequency Access Point station integrated into the wireless LAN and the distribution system Portal bridge to other (wired) networks Distribution System interconnection network to form one logical network (EES: Extended Service Set) based on several BSS LAN 802.x LAN STA1 BSS1 Portal Access Point Distribution System Access Point ESS BSS2 STA2 STA3 LAN Infrastructure-based Prof. Dr.-Ing. Jochen Schiller 9

Extended Service Set (ESS) and has its own identifier, the ESSID
Extended Service Set (ESS) and has its own identifier, the ESSID. The ESSID is the ‘name’ of a network and is used to separate different networks. Without knowing the ESSID (and assuming no hacking) it should not be possible to participate in the WLAN. Stations can select an AP and associate with it. The APs support roaming (i.e., changing access points), the distribution system handles data transfer between the different APs. APs provide synchronization within a BSS. In addition to infrastructure-based networks, IEEE allows the building of ad-hoc networks

ARCHITECTURE OF AN AD-HOC NETWORK
Direct communication within a limited range Station (STA): terminal with access mechanisms to the wireless medium Independent Basic Service Set (IBSS): group of stations using the same radio frequency In this case, an IBSS comprises a group of stations using the same radio frequency. This means for example that STA3 can communicate directly with STA2 but not with STA5. LAN STA1 IBSS1 STA3 STA2 IBSS2 STA5 STA4 LAN

PROTOCOL ARCHITECTURE
Applications should not notice any difference apart from the lower bandwidth and perhaps higher access time from the wireless LAN. The WLAN behaves like a slow wired LAN. The higher layers (application, TCP, IP) look the same for wireless nodes as for wired nodes. An IEEE wireless LAN connected to a switched IEEE ethernet via a bridge.

The IEEE standard only covers the physical layer PHY and medium access layer MAC like the other 802.x LANs do. The physical layer is subdivided into the physical layer convergence protocol (PLCP) and the physical medium dependent sublayer PMD The main tasks of the PHY management include channel tuning and PHY MIB maintenance. PLCP sublayer provides a carrier sense signal, called clear channel assessment (CCA), and provides a common PHY service access point (SAP) independent of the transmission technology. Finally, the PMD sublayer handles modulation and encoding/decoding of signals. The basic tasks of the MAC layer comprise medium access, fragmentation of user data, and encryption.

PHYSICAL LAYER: IEEE supports three different physical layers: One layer based on infra red Two layers based on radio transmission The PHY layer offers a service access point (SAP) with 1 or 2 Mbit/s transfer rate to the MAC layer. THREE VERSIONS OF PHY LAYER: Frequency Hopping Spread Spectrum Direct Sequence Spread Spectrum Infra Red } Radio Transmission

Frequency Hopping Spread Spectrum
Frequency hopping spread spectrum (FHSS) is a spread spectrum technique which allows for the coexistence of multiple networks in the same area by separating different networks using different hopping sequences. The original standard defines 79 hopping channels for North America and Europe, and 23 hopping channels for Japan. The selection of a particular channel is achieved by using a pseudo-random hopping pattern. The standard specifies Gaussian shaped FSK (frequency shift keying), GFSK, as modulation for the FHSS PHY. For 1 Mbit/s a 2 level GFSK is used (i.e., 1 bit is mapped to one frequency), a 4 level GFSK for 2 Mbit/s (i.e., 2 bits are mapped to one frequency). While sending and receiving at 1 Mbit/s is mandatory for all devices, operation at 2 Mbit/s is optional. This facilitated the production of low-cost devices for the lower rate only and more powerful devices for both transmission rates in the early days of

Format of an IEEE 802.11 PHY frame using FHSS
Synchronization: This pattern is used for synchronization of potential receivers and signal detection by the CCA. Start frame delimiter (SFD): The following 16 bits indicate the start of the frame and provide frame synchronization. PLCP_PDU length word (PLW): This first field of the PLCP header indicates the length of the payload in bytes PLCP signalling field (PSF): This 4 bit field indicates the data rate of the payload following. Header error check (HEC): Finally, the PLCP header is protected by a 16 bit checksum

Direct sequence spread spectrum
Direct sequence spread spectrum (DSSS) is the alternative spread spectrum method separating by code and not by frequency. In the case of IEEE DSSS, spreading is achieved using the 11-chip Barker sequence (+1, –1, +1, +1, –1, +1, +1, +1, –1, –1, –1). The key characteristics of this method are its robustness against interference and its insensitivity to multipath propagation. However, the implementation is more complex compared to FHSS. The system uses differential binary phase shift keying (DBPSK) for 1 Mbit/s transmission and differential quadrature phase shift keying (DQPSK) for 2 Mbit/s as modulation schemes.

Format of an IEEE 802.11 PHY frame using DSSS
Synchronization: The first 128 bits are not only used for synchronization, but also gain setting, energy detection (for the CCA), and frequency offset compensation. Start frame delimiter (SFD): This 16 bit field is used for synchronization at the beginning of a frame Signal: Only two values have been defined for this field to indicate the data rate of the payload. The value 0x0A indicates 1 Mbit/s (and thus DBPSK), 0x14 indicates 2 Mbit/s (and thus DQPSK). Service: This field is reserved for future use Length: 16 bits are used in this case for length indication of the payload in microseconds. Header error check (HEC): Signal, service, and length fields are protected by this checksum.

Infra Red The PHY layer, which is based on infra red (IR) transmission, uses near visible light at 850–950 nm. The standard does not require a line-of-sight between sender and receiver, but should also work with diffuse light. This allows for point-to-multipoint communication. The maximum range is about 10 m if no sunlight or heat sources interfere with the transmission. Typically, such a network will only work in buildings, e.g., classrooms, meeting rooms etc. Today, no products are available that offer infra red communication based on Proprietary products offer, e.g., up to 4 Mbit/s using diffuse infra red light. Alternatively, directed infra red communication based on IrDA can be used (IrDA, 2002).

Medium access control layer
It has to control medium access, but it can also offer support for roaming, authentication, and power conservation. The basic services provided by the MAC layer are the mandatory asynchronous data service and an optional time-bounded service. While only offers the asynchronous service in ad-hoc network mode, both service types can be offered using an infrastructure-based network together with the access point coordinating medium access.

The following three basic access mechanisms have been defined for IEEE 802.11:
The mandatory basic method based on a version of CSMA/CA An optional method avoiding the hidden terminal problem A contention-free polling method for time-bounded service. DCF only offers asynchronous service, while PCF offers both asynchronous and time-bounded. The MAC mechanisms are also called distributed foundation wireless medium access control (DFWMAC). } distributed coordination function (DCF) point coordination function (PCF).

Medium access and inter-frame spacing
Short inter-frame spacing (SIFS): The shortest waiting time for medium access (so the highest priority) is defined for short control messages, such as acknowledgements of data packets or polling responses. PCF inter-frame spacing (PIFS): A waiting time between DIFS and SIFS (and thus a medium priority) is used for a time-bounded service. DCF inter-frame spacing (DIFS): This parameter denotes the longest waiting time and has the lowest priority for medium access. This waiting time is used for asynchronous data service within a contention period

1.Basic DFWMAC-DCF using CSMA/CA
Station ready to send starts sensing the medium (carrier sense based on CCA, clear channel assessment) If the medium is free for the duration of an inter-frame space (IFS), the station can start sending (IFS depends on service type) If the medium is busy, the station has to wait for a free IFS, then the station must additionally wait a random back-off time (collision avoidance, multiple of slot-time) CW = 7, 15, 31, 63, 127 If another station occupies the medium during the back-off time of the station, the back-off timer stops (fairness)

802.11 - competing stations - simple version (no RTS/CTS)
Freie Universität Berlin Institut of Computer Science Mobile Communications 2002 competing stations - simple version (no RTS/CTS) DIFS DIFS DIFS DIFS boe bor boe bor boe busy station1 boe busy station2 busy station3 boe busy boe bor station4 boe bor boe busy boe bor station5 t busy medium not idle (frame, ack etc.) boe elapsed backoff time packet arrival at MAC bor residual backoff time Prof. Dr.-Ing. Jochen Schiller

802.11 - CSMA/CA access method II
Freie Universität Berlin Institut of Computer Science Mobile Communications 2002 CSMA/CA access method II Sending unicast packets Station has to wait for DIFS before sending data Receivers acknowledge at once (after waiting for SIFS) if the packet was received correctly (CRC) Automatic retransmission of data packets in case of transmission errors DIFS data sender SIFS ACK receiver DIFS data other stations t waiting time contention Prof. Dr.-Ing. Jochen Schiller

2. 802.11 – DFWMAC (Distributed Foundation Wireless MAC)
Freie Universität Berlin Institut of Computer Science Mobile Communications 2002 – DFWMAC (Distributed Foundation Wireless MAC) Sending unicast packets Station can send RTS with reservation parameter after waiting for DIFS (reservation determines amount of time the data packet needs the medium) Acknowledgement via CTS after SIFS by receiver (if ready to receive) Sender can now send data at once, acknowledgement via ACK Other stations store medium reservations distributed via RTS and CTS DIFS RTS data sender SIFS SIFS SIFS CTS ACK receiver DIFS NAV (RTS) data other stations NAV (CTS) t defer access contention NAV – Network Allocation Vector Prof. Dr.-Ing. Jochen Schiller

The RTS packet includes the receiver of the data transmission to come and the duration of the whole data transmission. This duration specifies the time interval necessary to transmit the whole data frame and the acknowledgement related to it. Every node receiving this RTS now has to set its net allocation vector (NAV) in accordance with the duration field.

Mobile Communications 2002 Fragmentation DIFS RTS frag1 frag2 sender SIFS SIFS SIFS SIFS SIFS CTS ACK1 ACK2 receiver NAV (RTS) NAV (CTS) DIFS NAV (frag1) data other stations NAV (ACK1) t contention Prof. Dr.-Ing. Jochen Schiller

3. DFWMAC-PCF with polling
The two access mechanisms presented so far cannot guarantee a maximum access delay or minimum transmission bandwidth. To provide a time-bounded service, the standard specifies a point coordination function (PCF) on top of the standard DCF mechanisms. Using PCF requires an access point that controls medium access and polls the single nodes. Ad-hoc networks cannot use this function.

Mobile Communications 2002 DFWMAC-PCF PIFS stations‘ NAV wireless stations point coordinator D1 U1 SIFS D2 U2 SuperFrame t0 medium busy t1 contention free period Prof. Dr.-Ing. Jochen Schiller

Mobile Communications 2002 DFWMAC-PCF II (cont.) t stations‘ NAV wireless stations point coordinator D3 PIFS D4 U4 SIFS CFend contention period contention free period t2 t3 t4 CFend - contention free period end Prof. Dr.-Ing. Jochen Schiller

MAC frames Frame control: The first 2 bytes serve several purposes. They contain several sub-fields as explained after the MAC frame. Duration/ID: The duration field contains the value indicating the period of time in which the medium is occupied (in μs). Address 1 to 4: The four address fields contain standard IEEE 802 MAC addresses (48 bit each), as they are known from other 802.x LANs. Sequence control: Due to the acknowledgement mechanism frames may be duplicated. Therefore a sequence number is used to filter duplicates. Data: The MAC frame may contain arbitrary data (max. 2,312 byte), which is transferred transparently from a sender to the receiver(s).

Checksum (CRC): Finally, a 32 bit checksum is used to protect the frame as it is common practice in all 802.x networks. Protocol version: This 2 bit field indicates the current protocol version and is fixed to 0 by now. Type: The type field determines the function of a frame: management (=00), control (=01), or data (=10). The value 11 is reserved Subtype: Example subtypes for management frames are: 0000 for association request, 1000 for beacon. More fragments: This field is set to 1 in all data or management frames that have another fragment of the current. Retry: If the current frame is a retransmission of an earlier frame, this bit is set to 1. With the help of this bit it may be simpler for receivers to eliminate duplicate frames. Power management: This field indicates the mode of a station after successful transmission of a frame. Set to 1 the field indicates that the station goes into power-save mode. If the field is set to 0, the station stays active. More data: In general, this field is used to indicate a receiver that a sender has more data to send than the current frame. Wired equivalent privacy (WEP): This field indicates that the standard security mechanism of is applied. Order: If this bit is set to 1 the received frames must be processed in strict order.

MAC management Mobile Communications 2002 Synchronization try to find a WLAN, try to stay within a WLAN timer etc. Power management sleep-mode without missing a message periodic sleep, frame buffering, traffic measurements Association/Reassociation integration into a LAN roaming, i.e. change networks by changing access points scanning, i.e. active search for a network MIB - Management Information Base managing, read, write (SNMP) Prof. Dr.-Ing. Jochen Schiller

Synchronization using a Beacon (infrastructure)
Freie Universität Berlin Institut of Computer Science Mobile Communications 2002 Synchronization using a Beacon (infrastructure) beacon interval access point B B B B busy busy busy busy medium t B value of the timestamp beacon frame (BSSID, Timestamp) Prof. Dr.-Ing. Jochen Schiller

Synchronization using a Beacon (ad-hoc)
Freie Universität Berlin Institut of Computer Science Mobile Communications 2002 Synchronization using a Beacon (ad-hoc) beacon interval B1 B1 station1 B2 B2 station2 busy busy busy busy medium t B value of the timestamp beacon frame random delay Prof. Dr.-Ing. Jochen Schiller

Mobile Communications 2002 Power management Idea: switch the transceiver off if not needed States of a station: sleep and awake Timing Synchronization Function (TSF) stations wake up at the same time Infrastructure Traffic Indication Map (TIM) list of unicast receivers transmitted by AP Delivery Traffic Indication Map (DTIM) list of broadcast/multicast receivers transmitted by AP Ad-hoc Ad-hoc Traffic Indication Map (ATIM) announcement of receivers by stations buffering frames more complicated - no central AP collision of ATIMs possible (scalability?) Prof. Dr.-Ing. Jochen Schiller

Power saving with wake-up patterns (infrastructure)
Freie Universität Berlin Institut of Computer Science Mobile Communications 2002 Power saving with wake-up patterns (infrastructure) TIM interval DTIM interval D B T T d D B access point busy busy busy busy medium p d station t T TIM D DTIM awake d data transmission to/from the station B broadcast/multicast p PS poll PS – Power Saving Traffic Indication Map (TIM) Delivery Traffic Indication Map (DTIM)-for multicast data transmission Prof. Dr.-Ing. Jochen Schiller

Power saving with wake-up patterns (ad-hoc)
Freie Universität Berlin Institut of Computer Science Mobile Communications 2002 Power saving with wake-up patterns (ad-hoc) ATIM window beacon interval B1 A D B1 station1 B2 B2 a d station2 t B A transmit ATIM D beacon frame random delay transmit data a d awake acknowledge ATIM acknowledge data Prof. Dr.-Ing. Jochen Schiller

Scanning Scanning involves the active search for a BSS. IEEE differentiates between passive and active scanning. Passive scanning - listening into the medium to find other networks, i.e., receiving the beacon of another network issued by access point. Active scanning - sending a probe on each channel and waiting for a response. Beacon and probe responses contain the information necessary to join the new BSS.

Active Scanning

802.11b Some companies offered proprietary solutions with 11 Mbit/s.
This standard describes a new PHY layer and is by far the most successful version of IEEE available today. All the MAC schemes, management procedures etc. are still same. Depending on the current interference and the distance between sender and receiver b systems offer 11, 5.5, 2, or 1 Mbit/s. Maximum user data rate is approx. 6 Mbit/s. The lower data rates 1 and 2 Mbit/s use the 11-chip Barker sequence The standard defines several packet formats for the physical layer. The mandatory format interoperates with the original versions of The optional versions provide a more efficient data transfer

long PLCP PPDU: One difference is the rate encoded in the signal field this is encoded in multiples of 100 kbit/s. 0x0A represents 1 Mbit/s 0x14 is used for 2 Mbit/s 0x37 for 5.5 Mbit/s 0x6E for 11 Mbit/s. Short PLCP PPDU: The short synchronization field consists of 56 scrambled zeros instead of scrambled ones. The length of the overhead is only half for the short frames (96 μs instead of 192 μs).

Channel plan for IEEE b

IEEE 802.11b non-overlapping channel selection
The spacing between the center frequencies should be at least 25 MHz This results in the channels 1, 6, and 11 for the US/Canada or 1, 7, 13 for Europe, respectively. It may be the case that, e.g., travellers from the US cannot use the additional channels (12 and 13) in Europe as their hardware is limited to 11 channels.

802.11a Initially aimed at the US 5 GHz U-NII (Unlicensed National Information Infrastructure) bands IEEE a offers up to 54 Mbit/s using OFDM. ETSI (Europe) defines different frequency bands for Europe: 5.15–5.35 GHz and 5.47–5.725 GHz It requires two additional mechanisms for operation: dynamic frequency selection (DFS) and transmit power control (TPC) Japan allows operation in the frequency range 5.15–5.25 GHz and requires carrier sensing every 4 ms to minimize interference. To be able to offer data rates up to 54 Mbit/s IEEE a uses many different technologies. The system uses 52 subcarriers (48 data + 4 pilot) that are modulated using BPSK, QPSK, 16-QAM, or 64-QAM. To mitigate transmission errors, FEC is applied using coding rates of 1/2, 2/3, or 3/4. To offer a data rate of 12 Mbit/s, 96 bits are coded into one OFDM symbol. These 96 bits are distributed over 48 subcarriers and 2 bits are modulated per sub-carrier using QPSK

WLAN: IEEE 802.11 – developments
Freie Universität Berlin Institut of Computer Science Mobile Communications 2002 WLAN: IEEE – developments 802.11c: Bridge Support Definition of MAC procedures to support bridges as extension to 802.1D 802.11d: Regulatory Domain Update Support of additional regulations related to channel selection, hopping sequences 802.11e: MAC Enhancements – QoS Enhance the current MAC to expand support for applications with Quality of Service requirements, and in the capabilities and efficiency of the protocol Definition of a data flow (“connection”) with parameters like rate, burst, period… Additional energy saving mechanisms and more efficient retransmission 802.11f: Inter-Access Point Protocol Establish an Inter-Access Point Protocol for data exchange via the distribution system 802.11g: Data Rates > 20 Mbit/s at 2.4 GHz; 54 Mbit/s, OFDM Successful successor of b, performance loss during mixed operation with 11b 802.11h: Spectrum Managed a Extension for operation of a in Europe by mechanisms like channel measurement for dynamic channel selection (DFS, Dynamic Frequency Selection) and power control (TPC, Transmit Power Control) Prof. Dr.-Ing. Jochen Schiller

WLAN: IEEE 802.11– developments
802.11i: Enhanced Security Mechanisms Enhance the current MAC to provide improvements in security. TKIP enhances the insecure WEP, but remains compatible to older WEP systems AES provides a secure encryption method and is based on new hardware 802.11j: Extensions for operations in Japan Changes of a for operation at 5GHz in Japan using only half the channel width at larger range 802.11k: Methods for channel measurements Devices and access points should be able to estimate channel quality in order to be able to choose a better access point of channel 802.11m: Updates of the standards 802.11n: Higher data rates above 100Mbit/s Changes of PHY and MAC with the goal of 100Mbit/s at MAC SAP MIMO antennas (Multiple Input Multiple Output), up to 600Mbit/s are currently feasible However, still a large overhead due to protocol headers and inefficient mechanisms 802.11p: Inter car communications Communication between cars/road side and cars/cars Planned for relative speeds of min. 200km/h and ranges over 1000m Usage of GHz band in North America

WLAN: IEEE 802.11– future developments
802.11r: Faster Handover between BSS Secure, fast handover of a station from one AP to another within an ESS Current mechanisms (even newer standards like i) plus incompatible devices from different vendors are massive problems for the use of, e.g., VoIP in WLANs Handover should be feasible within 50ms in order to support multimedia applications efficiently 802.11s: Mesh Networking Design of a self-configuring Wireless Distribution System (WDS) based on Support of point-to-point and broadcast communication across several hops 802.11t: Performance evaluation of networks Standardization of performance measurement schemes 802.11u: Interworking with additional external networks 802.11v: Network management Extensions of current management functions, channel measurements Definition of a unified interface 802.11w: Securing of network control Classical standards like , but also i protect only data frames, not the control frames. Thus, this standard should extend i in a way that, e.g., no control frames can be forged.

(High Performance Local Area Network)
HIPERLAN (High Performance Local Area Network)

WLAN allowing for node mobility and supporting ad-hoc and infrastructure-based topologies
Names have changed and the former HIPERLANs 2, 3, and 4 are now called HiperLAN2, HIPERACCESS, and HIPERLINK. The current focus is on HiperLAN2, a standard that comprises many elements from ETSI’s BRAN (broadband radio access networks) and wireless ATM activities. Neither wireless ATM nor HIPERLAN 1 were a commercial success.

Historical: HIPERLAN 1 Wireless LAN supporting priorities and packet life time for data transfer at 23.5 Mbit/s, including forwarding mechanisms, topology discovery, user data encryption, network identification and power conservation mechanisms. HIPERLAN 1 should operate at 5.1–5.3 GHz with a range of 50 m in buildings at 1 W transmit power. The service offered by a HIPERLAN 1 is compatible with the standard MAC services known from IEEE 802.x LANs. For power conservation, a node may set up a specific wake-up pattern. This pattern determines at what time the node is ready to receive, so that at other times, the node can turn off its receiver and save energy. These nodes are called p-savers and need so-called p-supporters that contain information about the wake-up patterns of all the p-savers they are responsible for. A p-supporter only forwards data to a p-saver at the moment the p-saver is awake.

Elimination-yield non-preemptive priority multiple access (EY-NPMA)
It is a heart of the channel access providing priorities and different access schemes. EY-NPMA divides the medium access of different competing nodes into three phases: Prioritization: Determine the highest priority of a data packet ready to be sent by competing nodes. Contention: Eliminate all but one of the contenders, if more than one sender has the highest current priority. Transmission: Finally, transmit the packet of the remaining node. IPS IPA IES IESV IYS transmission synchronization prioritization contention transmission The contention phase is further subdivided into an elimination phase and a yield phase. elimination survival verification priority detection priority assertion elimination burst user data yield listening t

EY-NPMA (Elimination Yield Non-preemptive Priority Multiple Access)
3 phases: priority resolution, contention resolution, transmission Finding the highest priority Every priority corresponds to a time-slot to send in the first phase, the higher the priority the earlier the time-slot to send Higher priorities can not be preempted If an earlier time-slot for a higher priority remains empty, stations with the next lower priority might send After this first phase the highest current priority has been determined

Several terminals can now have the same priority and wish to send
CONTENTION PHASE Elimination Burst: all remaining terminals send a burst to eliminate contenders ( , high bit- rate) Elimination Survival Verification: contenders now sense the channel, if the channel is free they can continue, otherwise they have been eliminated Yield Listening: contenders again listen in slots with a nonzero probability, if the terminal senses its slot idle it is free to transmit at the end of the contention DATA TRANSMISSION The winner can now send its data (however, a small chance of collision remains).if the channel was idle for a longer time a terminal can send at once without using EY-NPMA synchronization using the last data transmission

(Wireless Asynchronous Transfer Mode)
Wireless ATM (Wireless Asynchronous Transfer Mode)

WATM: sometimes also called wireless, mobile ATM, wmATM
IEEE WLANs originate from the data communication community, many WATM aspects come from the telecommunication industry Motivation for WATM: The need for seamless integration of wireless terminals into an ATM network. ATM networks scale well from LANs to WANs – and mobility is needed in local and wide area applications. For ATM to be successful, it must offer a wireless extension. WATM could offer QoS for adequate support of multi-media data streams.

Wireless ATM working group:
ATM Forum formed the Wireless ATM Working Group in 1996, which aimed to develop a set of specifications that extends the use of ATM technology to wireless networks. The following more general extensions of the ATM system also need to be considered for a mobile ATM: Location management: Similar to other cellular networks, WATM networks must be able to locate a wireless terminal or a mobile user. Mobile routing: Even if the location of a terminal is known to the system, it still has to route the traffic through the network to the access point currently responsible for the wireless terminal. Each time a user moves to a new access point, the system must reroute traffic. Handover signalling: The network must provide mechanisms which search for new access points QoS and traffic control: In contrast to wireless networks offering only best effort traffic, and to cellular networks offering only a few different types of traffic, WATM should be able to offer many QoS parameters. To maintain these parameters, all actions such as rerouting, handover etc. have to be controlled. Network management: All extensions of protocols or other mechanisms also require an extension of the management functions to control the network

WATM services: Office environments Universities, schools, training centre Industry Hospitals Home Networked vehicles

Generic reference model
WATM terminal adapter MATM terminal RAS EMAS -E -N ATM- Switch fixed end system radio segment fixed network segment A mobile ATM (MATM) terminal uses a WATM terminal adapter to gain wireless access to a WATM RAS (Radio Access System). MATM terminals could be represented by, e.g., laptops using an ATM adapter for wired access plus software for mobility. The WATM terminal adapter enables wireless access, i.e., it includes the transceiver etc., but it does not support mobility. The RAS with the radio transceivers is connected to a mobility enhanced ATM switch (EMAS-E), which in turn connects to the ATM network with mobility aware switches (EMAS-N) Finally, a wired, non-mobility aware ATM end system may be the communication partner in this example.

HANDOVER: The main problem for WATM during the handover is rerouting all connections and maintaining connection quality. Different requirements have been set up for handover Handover of multiple connections: Handover in WATM must support more than one connection. This results in the rerouting of every connection after handover. However, resource availability may not allow rerouting of all connections or forces QoS degradation. The terminal may then decide to accept a lower quality or to drop single connections. Handover of point-to-multi-point connections: WATM handover should also support these types of connection. However, due to the complexity of the scheme, some restrictions might be necessary. QoS support: Handover should aim to preserve the QoS of all connections during handover. However, due to limited resources, this is not always possible.

MOBILE QUALITY OF SERVICE
LOCATION MANAGEMENT As for all networks supporting mobility, special functions are required for looking up the current position of a mobile terminal, for providing the moving terminal with a permanent address, and for ensuring security features such as privacy, authentication, or authorization. MOBILE QUALITY OF SERVICE Wired QoS: The infrastructure network needed for WATM has the same QoS properties as any wired ATM network. Wireless QoS: The QoS properties of the wireless part of a WATM network differ from those of the wired part. Channel reservation and multiplexing mechanisms at the air interface strongly influence cell delay variation. Handover QoS: A new set of QoS parameters are introduced by handover. For example, handover blocking due to limited resources at target access points, cell loss during handover

Hard handover QoS: While the QoS with the current RAS may be guaranteed due to the current availability of resources, no QoS guarantees are given after the handover. Soft handover QoS: Even for the current wireless segment, only statistical QoS guarantees can be given, and the applications also have to adapt after the handover.

Broadband Radio Access Networks
BRAN Broadband Radio Access Networks

The main motivation behind BRAN is the deregulation and privatization of the telecommunication sector in Europe. Many new providers experience problems getting access to customers because the telephone infrastructure belongs to a few big companies. One possible technology to provide network access for customers is radio. The advantages of radio access are high flexibility and quick installation. BRAN standardization has a rather large scope including indoor and campus mobility, transfer rates of 25–155 Mbit/s, and a transmission range of 50 m–5 km.

BROADBAND NETWORK TYPES
HIPERLAN/2 short range (< 200 m), indoor/campus, 25 Mbit/s user data rate access to telecommunication systems, multimedia applications, mobility (<10 m/s) HIPERACCESS wider range (< 5 km), outdoor, 25 Mbit/s user data rate fixed radio links to customers (“last mile”), alternative to xDSL or cable modem, quick installation Several (proprietary) products exist with 155 Mbit/s plus QoS HIPERLINK – currently no activities intermediate link, 155 Mbit/s connection of HIPERLAN access points or connection between HIPERACCESS nodes

HiperLAN2

This wireless network works at 5 GHz and offers data rates of up to 54 Mbit/s including QoS support and enhanced security features.

Reference model and configurations
Sector handover (Inter sector): If sector antennas are used for an AP, which is optional in the standard, the AP shall support sector handover. This type of handover is handled inside the DLC layer so is not visible outside the AP Radio handover (Inter-APT/Intra-AP): As this handover type, too, is handled within the AP, no external interaction is needed. In the example of Figure the terminal MT3, moves from one APT to another of the same AP. All context data for the connections are already in the AP Network handover (Inter-AP/Intra-network): This is the most complex situation: MT2 moves from one AP to another. In this case, the core network and higher layers are also involved. This handover might be supported by the core network AP MT1 Core Network (Ethernet, Firewire, ATM, UMTS) APT APC 1 MT2 3 AP MT3 APT APC 2 MT4 APT

Centralized vs. direct mode
AP AP/CC control control control data MT1 MT2 MT1 MT2 MT1 data MT2 +CC data control Centralized Direct

HiperLAN2 protocol stack
Higher layers Convergence layer DLC control SAP DLC user SAP Radio link control sublayer Data link control - basic data transport function Radio resource control Assoc. control DLC conn. control Scope of HiperLAN2 standards Error control Radio link control Medium access control Physical layer

Physical layer reference configuration
PDU train from DLC (PSDU) scrambling FEC coding interleaving mapping OFDM PHY bursts (PPDU) radio transmitter Scrambling of all data bits with the generator polynomial for DC blocking and whitening of the spectrum. FEC coding for error protection For mitigation of frequency selective fading interleaving is applied. mapping process first divides the bit sequence in groups of 1,2, 4, or 6 bits depending on the modulation scheme (BPSK, QPSK, 16-QAM, or 64-QAM). The OFDM modulation step converts these symbols into a baseband signal with the help of the inverse FFT. Creation of PHY bursts Each burst consists of a preamble and a payload. radio transmission shifts the baseband signal to a carrier frequency depending on the channel number

Operating channels of HiperLAN2 in Europe
36 40 44 48 52 56 60 64 channel 5150 5180 5200 5220 5240 5260 5280 5300 5320 5350 [MHz] 16.6 MHz 100 104 108 112 116 120 124 128 132 136 140 channel 5470 5500 5520 5540 5560 5580 5600 5620 5640 5660 5680 5700 5725 16.6 MHz [MHz] center frequency = *channel number [MHz]

Basic structure of HiperLAN2 MAC frames
2 ms 2 ms 2 ms 2 ms TDD, 500 OFDM symbols per frame MAC frame MAC frame MAC frame MAC frame . . . broadcast phase downlink phase uplink phase random access phase variable variable variable 2 406 24 bit LCH PDU type payload CRC LCH transfer syntax 2 10 396 24 bit LCH PDU type sequence number payload CRC UDCH transfer syntax (long PDU) 54 byte

Valid configurations of HiperLAN2 MAC frames
2 ms 2 ms 2 ms 2 ms MAC frame MAC frame MAC frame MAC frame . . . random access broadcast downlink uplink BCH FCH ACH DL phase DiL phase UL phase RCHs Valid combinations of MAC frames for a single sector AP BCH FCH ACH DiL phase UL phase RCHs BCH FCH ACH DL phase UL phase RCHs BCH FCH ACH UL phase RCHs BCH FCH ACH DL phase DiL phase RCHs BCH FCH ACH DiL phase RCHs BCH FCH ACH DL phase RCHs BCH FCH ACH RCHs

Mapping of logical and transport channels
BCCH FCCH RFCH LCCH RBCH DCCH UDCH UBCH UMCH downlink BCH FCH ACH SCH LCH UDCH DCCH LCCH ASCH UDCH UBCH UMCH DCCH RBCH LCCH LCH SCH RCH LCH SCH uplink direct link

Mobile Communications 2002 Bluetooth Idea Universal radio interface for ad-hoc wireless connectivity Interconnecting computer and peripherals, handheld devices, PDAs, cell phones – replacement of IrDA Embedded in other devices, goal: 5€/device (2005: 40€/USB bluetooth) Short range (10 m), low power consumption, license-free 2.45 GHz ISM Voice and data transmission, approx. 1 Mbit/s gross data rate One of the first modules (Ericsson). Prof. Dr.-Ing. Jochen Schiller

Mobile Communications 2002 Bluetooth History 1994: Ericsson (Mattison/Haartsen), “MC-link” project Renaming of the project: Bluetooth according to Harald “Blåtand” Gormsen [son of Gorm], King of Denmark in the 10th century 1998: foundation of Bluetooth SIG, 1999: erection of a rune stone at Ercisson/Lund ;-) 2001: first consumer products for mass market, spec. version 1.1 released 2005: 5 million chips/week Special Interest Group Original founding members: Ericsson, Intel, IBM, Nokia, Toshiba Added promoters: 3Com, Agere (was: Lucent), Microsoft, Motorola > 2500 members Common specification and certification of products (was: ) Prof. Dr.-Ing. Jochen Schiller

Mobile Communications 2002 History and hi-tech… 1999: Ericsson mobile communications AB reste denna sten till minne av Harald Blåtand, som fick ge sitt namn åt en ny teknologi för trådlös, mobil kommunikation. Prof. Dr.-Ing. Jochen Schiller

…and the real rune stone
Freie Universität Berlin Institut of Computer Science Mobile Communications 2002 …and the real rune stone Located in Jelling, Denmark, erected by King Harald “Blåtand” in memory of his parents. The stone has three sides – one side showing a picture of Christ. Inscription: "Harald king executes these sepulchral monuments after Gorm, his father and Thyra, his mother. The Harald who won the whole of Denmark and Norway and turned the Danes to Christianity." This could be the “original” colors of the stone. Inscription: “auk tani karthi kristna” (and made the Danes Christians) Btw: Blåtand means “of dark complexion” (not having a blue tooth…) Prof. Dr.-Ing. Jochen Schiller

Mobile Communications 2002 Characteristics 2.4 GHz ISM band, 79 (23) RF channels, 1 MHz carrier spacing Channel 0: 2402 MHz … channel 78: 2480 MHz G-FSK modulation, mW transmit power FHSS and TDD Frequency hopping with 1600 hops/s Hopping sequence in a pseudo random fashion, determined by a master Time division duplex for send/receive separation Voice link – SCO (Synchronous Connection Oriented) FEC (forward error correction), no retransmission, 64 kbit/s duplex, point-to-point, circuit switched Data link – ACL (Asynchronous ConnectionLess) Asynchronous, fast acknowledge, point-to-multipoint, up to kbit/s symmetric or 723.2/57.6 kbit/s asymmetric, packet switched Topology Overlapping piconets (stars) forming a scatternet Prof. Dr.-Ing. Jochen Schiller

Mobile Communications 2002 Piconet Collection of devices connected in an ad hoc fashion One unit acts as master and the others as slaves for the lifetime of the piconet Master determines hopping pattern, slaves have to synchronize Each piconet has a unique hopping pattern Participation in a piconet = synchronization to hopping sequence Each piconet has one master and up to 7 simultaneous slaves (> 200 could be parked) 3 bit address is used by Bluetooth device. P S S M P SB S P SB M=Master S=Slave P=Parked SB=Standby Prof. Dr.-Ing. Jochen Schiller

Mobile Communications 2002 Forming a piconet All devices in a piconet hop together Master gives slaves its clock and device ID Hopping pattern: determined by device ID (48 bit, unique worldwide) Phase in hopping pattern determined by clock Addressing Active Member Address (AMA, 3 bit) Parked Member Address (PMA, 8 bit)    P  S SB  SB  S   SB   M P SB SB    SB  S   SB SB  P  SB SB SB Prof. Dr.-Ing. Jochen Schiller

Mobile Communications 2002 Scatternet Linking of multiple co-located piconets through the sharing of common master or slave devices Devices can be slave in one piconet and master of another Communication between piconets Devices jumping back and forth between the piconets Piconets (each with a capacity of 720 kbit/s) P S S S P P M=Master S=Slave P=Parked SB=Standby M M SB S P SB SB S Prof. Dr.-Ing. Jochen Schiller

Bluetooth protocol stack
Freie Universität Berlin Institut of Computer Science Mobile Communications 2002 Bluetooth protocol stack audio apps. NW apps. vCal/vCard telephony apps. mgmnt. apps. TCP/UDP OBEX AT modem commands TCS BIN SDP Control IP BNEP PPP Audio RFCOMM (serial line interface) Logical Link Control and Adaptation Protocol (L2CAP) Host Controller Interface Link Manager Baseband OBEX tb é usado sovre IrDA para aplicações de vCard e vCalendar Radio AT: attention sequence OBEX: object exchange TCS BIN: telephony control protocol specification – binary BNEP: Bluetooth network encapsulation protocol SDP: service discovery protocol RFCOMM: radio frequency comm. Prof. Dr.-Ing. Jochen Schiller

Radio layer Power class 1: Maximum power is 100 mW and minimum is 1 mW (typ. 100 m range without obstacles). Power control is mandatory. Power class 2: Maximum power is 2.5 mW, nominal power is 1 mW, and minimum power is 0.25 mW (typ. 10 m range without obstacles). Power control is optional. Power class 3: Maximum power is 1 mW.

Mobile Communications 2002 Baseband Piconet/channel definition Low-level packet definition Access code Channel, device access, e.g., derived from master address (48-bit) Packet header 1/3-FEC, active member address (broadcast + 7 slaves), link type, alternating bit ARQ/SEQ, checksum 68(72) 54 0-2745 bits access code packet header payload 4 64 (4) 3 4 1 1 1 8 bits preamble sync. (trailer) AM address type flow ARQN SEQN HEC Prof. Dr.-Ing. Jochen Schiller

Frequency selection during data transmission
fk fk+1 fk+2 fk+3 fk+4 fk+5 fk+6 M S M S M S M t fk fk+3 fk+4 fk+5 fk+6 M S M S M t fk fk+1 fk+6 M S M t

SCO payload types payload (30) HV1 audio (10) FEC (20) HV2 audio (20)
DV audio (10) header (1) payload (0-9) 2/3 FEC CRC (2) (bytes)

ACL Payload types payload (0-343) header (1/2) payload (0-339) CRC (2)
DM1 header (1) payload (0-17) 2/3 FEC CRC (2) DH1 header (1) payload (0-27) CRC (2) (bytes) DM3 header (2) payload (0-121) 2/3 FEC CRC (2) DH3 header (2) payload (0-183) CRC (2) DM5 header (2) payload (0-224) 2/3 FEC CRC (2) DH5 header (2) payload (0-339) CRC (2) AUX1 header (1) payload (0-29)

Mobile Communications 2002 Baseband link types Polling-based TDD packet transmission 625µs slots, master polls slaves SCO (Synchronous Connection Oriented) – Voice Periodic single slot packet assignment, 64 kbit/s full-duplex, point-to-point ACL (Asynchronous ConnectionLess) – Data Variable packet size (1,3,5 slots), asymmetric bandwidth, point-to-multipoint SCO ACL SCO ACL SCO ACL SCO ACL MASTER f0 f4 f6 f8 f12 f14 f18 f20 SLAVE 1 f1 f7 f9 f13 f19 SLAVE 2 f5 f17 f21 Prof. Dr.-Ing. Jochen Schiller

Mobile Communications 2002 Robustness Slow frequency hopping with hopping patterns determined by a master Protection from interference on certain frequencies Separation from other piconets (FH-CDMA) Retransmission ACL only, very fast Forward Error Correction SCO and ACL Error in payload (not header!) NAK ACK MASTER A C C F H SLAVE 1 B D E SLAVE 2 G G Prof. Dr.-Ing. Jochen Schiller

Baseband states of a Bluetooth device
Freie Universität Berlin Institut of Computer Science Mobile Communications 2002 Baseband states of a Bluetooth device standby unconnected inquiry page connecting detach transmit AMA connected AMA active park PMA hold AMA sniff AMA low power Standby: do nothing Inquire: search for other devices Page: connect to a specific device Connected: participate in a piconet Park: release AMA, get PMA Sniff: listen periodically, not each slot Hold: stop ACL, SCO still possible, possibly participate in another piconet Prof. Dr.-Ing. Jochen Schiller

Example: Bluetooth/USB adapter (2002: 50€)

L2CAP - Logical Link Control and Adaptation Protocol
Freie Universität Berlin Institut of Computer Science Mobile Communications 2002 L2CAP - Logical Link Control and Adaptation Protocol Simple data link protocol on top of baseband Connection oriented, connectionless, and signalling channels Protocol multiplexing RFCOMM, SDP, telephony control Segmentation & reassembly Up to 64kbyte user data, 16 bit CRC used from baseband QoS flow specification per channel Follows RFC 1363, specifies delay, jitter, bursts, bandwidth Group abstraction Create/close group, add/remove member Prof. Dr.-Ing. Jochen Schiller

L2CAP logical channels Master Slave Slave L2CAP L2CAP L2CAP baseband
1 1 d d d d 1 1 d d 2 baseband baseband baseband signalling ACL connectionless connection-oriented

L2CAP packet formats Connectionless PDU 2 2 2 0-65533 bytes length
CID=2 PSM payload Connection-oriented PDU 2 2 bytes length CID payload Signalling command PDU 2 2 bytes length CID=1 One or more commands 1 1 2 0 code ID length data

Security Mobile Communications 2002 User input (initialization) PIN (1-16 byte) Pairing PIN (1-16 byte) Authentication key generation (possibly permanent storage) E2 E2 link key (128 bit) Authentication link key (128 bit) Encryption key generation (temporary storage) E3 E3 encryption key (128 bit) Encryption encryption key (128 bit) Keystream generator Keystream generator Ciphering payload key payload key Cipher data Data Data Prof. Dr.-Ing. Jochen Schiller

SDP – Service Discovery Protocol
Freie Universität Berlin Institut of Computer Science Mobile Communications 2002 SDP – Service Discovery Protocol Inquiry/response protocol for discovering services Searching for and browsing services in radio proximity Adapted to the highly dynamic environment Can be complemented by others like SLP, Jini, Salutation, … Defines discovery only, not the usage of services Caching of discovered services Gradual discovery Service record format Information about services provided by attributes Attributes are composed of an 16 bit ID (name) and a value values may be derived from 128 bit Universally Unique Identifiers (UUID) Prof. Dr.-Ing. Jochen Schiller

Additional protocols to support legacy protocols/apps.
Freie Universität Berlin Institut of Computer Science Mobile Communications 2002 Additional protocols to support legacy protocols/apps. RFCOMM Emulation of a serial port (supports a large base of legacy applications) Allows multiple ports over a single physical channel Telephony Control Protocol Specification (TCS) Call control (setup, release) Group management OBEX Exchange of objects, IrDA replacement WAP Interacting with applications on cellular phones Prof. Dr.-Ing. Jochen Schiller

WPAN: IEEE 802.15-1 – Bluetooth
Freie Universität Berlin Institut of Computer Science Mobile Communications 2002 WPAN: IEEE – Bluetooth Data rate Synchronous, connection-oriented: 64 kbit/s Asynchronous, connectionless 433.9 kbit/s symmetric 723.2 / 57.6 kbit/s asymmetric Transmission range POS (Personal Operating Space) up to 10 m with special transceivers up to 100 m Frequency Free 2.4 GHz ISM-band Security Challenge/response (SAFER+), hopping sequence Availability Integrated into many products, several vendors Connection set-up time Depends on power-mode Max. 2.56s, avg. 0.64s Quality of Service Guarantees, ARQ/FEC Manageability Public/private keys needed, key management not specified, simple system integration Special Advantages/Disadvantages Advantage: already integrated into several products, available worldwide, free ISM- band, several vendors, simple system, simple ad-hoc networking, peer to peer, scatternets Disadvantage: interference on ISM-band, limited range, max. 8 devices/network&master, high set-up latency Prof. Dr.-Ing. Jochen Schiller

Mobile Communications 2002 WPAN: IEEE : Coexistance Coexistence of Wireless Personal Area Networks (802.15) and Wireless Local Area Networks (802.11), quantify the mutual interference : High-Rate Standard for high-rate (20Mbit/s or greater) WPANs, while still low-power/low-cost Data Rates: 11, 22, 33, 44, 55 Mbit/s Quality of Service isochronous protocol Ad hoc peer-to-peer networking Security Low power consumption Low cost Designed to meet the demanding requirements of portable consumer imaging and multimedia applications Prof. Dr.-Ing. Jochen Schiller

WPAN: IEEE 802.15 – future developments 2
Several working groups extend the standard a: Alternative PHY with higher data rate as extension to Applications: multimedia, picture transmission b: Enhanced interoperability of MAC Correction of errors and ambiguities in the standard c: Alternative PHY at GHz Goal: data rates above 2 Gbit/s Not all these working groups really create a standard, not all standards will be found in products later …

WPAN: IEEE 802.15 – future developments 3
Freie Universität Berlin Institut of Computer Science Mobile Communications 2002 WPAN: IEEE – future developments 3 : Low-Rate, Very Low-Power Low data rate solution with multi-month to multi-year battery life and very low complexity Potential applications are sensors, interactive toys, smart badges, remote controls, and home automation Data rates of kbit/s, latency down to 15 ms Master-Slave or Peer-to-Peer operation Up to 254 devices or simpler nodes Support for critical latency devices, such as joysticks CSMA/CA channel access (data centric), slotted (beacon) or unslotted Automatic network establishment by the PAN coordinator Dynamic device addressing, flexible addressing format Fully handshaked protocol for transfer reliability Power management to ensure low power consumption 16 channels in the 2.4 GHz ISM band, 10 channels in the 915 MHz US ISM band and one channel in the European 868 MHz band Basis of the ZigBee technology – Prof. Dr.-Ing. Jochen Schiller

Emerging Technologies
WiMAX Emerging Technologies

Current Scenario Think about how you access the Internet today. There are basically three different options: Broadband access - In your home, you have either a DSL or cable modem. At the office, your company may be using a T1 or a T3 line. WiFi access - In your home, you may have set up a WiFi router that lets you surf the Web while you lounge with your laptop. On the road, you can find WiFi hot spots in restaurants, hotels, coffee shops and libraries. Dial-up access - If you are still using dial-up, chances are that either broadband access is not available, or you think that broadband access is too expensive.

Current Scenario The main problems with broadband access are that it is pretty expensive and it doesn't reach all areas. The main problem with WiFi access is that hot spots are very small, so coverage is sparse. What if there were a new technology that solved all of these problems? This new technology would provide: The high speed of broadband service. Wireless rather than wired access, so it would be a lot less expensive than cable or DSL and much easier to extend to suburban and rural areas. Broad coverage like the cell phone network instead of small WiFi hotspots.

Wireless Broadband This system is actually coming into being right now, and it is called WiMAX. WiMAX is short for Worldwide Interoperability for Microwave Access, and it also goes by the IEEE name Also known as Wireless Metropolitan Area Network (Wireless MAN). Offers an alternative to high bandwidth wired access networks like fiber optic, cable modems and DSL. Provides network access to buildings through exterior antennas communicating with radio base stations. Networks can be created in just weeks by deploying a small number of base stations on buildings or poles to create high capacity wireless access systems.

WiMax Vs. WiFi WiMAX operates on the same general principles as WiFi - it sends data from one computer to another via Radio signals. A computer (either a desktop or a laptop) equipped with WiMAX would receive data from the WiMAX transmitting station, probably using encrypted data keys to prevent unauthorized users from stealing access. The fastest WiFi connection can transmit up to 54 megabits per second under optimal conditions. WiMAX should be able to handle up to 70 megabits per second. Even once that 70 megabits is split up between several dozen businesses or a few hundred home users, it will provide at least the equivalent of cable-modem transfer rates to each user.

WiMax Vs. WiFi The biggest difference isn't speed; it's distance. WiMAX outdistances WiFi by miles. WiFi's range is about 100 feet (30 m). WiMAX will blanket a radius of 30 miles (50 km) with wireless access. The increased range is due to the frequencies used and the power of the transmitter. Of course, at that distance, terrain, weather and large buildings will act to reduce the maximum range in some circumstances, but the potential is there to cover huge tracts of land. WiMax is not designed to clash with WiFi, but to coexist with it. WiMax specifications also provides much better facilities than WiFi, providing higher bandwidth and high data security by the use of enhanced encryption schemes.

WiMAX is not Wi-Fi

Overview of IEEE

Sub-standards of IEEE IEEE Air interface for 10 to 66 GHz IEEE Coexistence of broadband wireless access systems IEEE Air interface for licensed frequencies, 2 to 11 GHz

Basics of IEEE IEEE standards are concerned with the air interface between a subscriber’s transceiver station and a base transceiver station The Physical Layer MAC Layer Convergence Layer

IEEE 802.16 Protocol Architecture

Physical Layer Specifies the frequency band, the modulation scheme, error-correction techniques, synchronization between transmitter and receiver, data rate and the multiplexing structure Both TDD and FDD alternatives support adaptive burst profiles in which modulation and coding options may be dynamically assigned on a burst-by-burst basis Three physical layer for services: Wireless MAN-SC2, Wireless MAN-OFDM and Wireless MAN-OFDMA

Medium Access Control Layer
Designed for point-to-multipoint broadband wireless access Addresses the need for very high bit rates, both uplink (to the base station) and downlink (from the base station) Services like multimedia and voice can run as MAC is equipped to accommodate both continuous and bursty traffic

Convergence Layer Provides functions specific to the service being provided Bearer services include digital audio/video multicast, digital telephony, ATM, Internet access, wireless trunks in telephone networks and frame relay

Reference Network Model
The IEEE e-2005 standard provides the air interface for WiMAX but does not define the full end-to- end WiMAX network. The WiMAX Forum's Network Working Group (NWG), is responsible for developing the end-to-end network requirements, architecture, and protocols for WiMAX, using IEEE e-2005 as the air interface. The WiMAX NWG has developed a network reference model to serve as an architecture framework for WiMAX deployments and to ensure interoperability among various WiMAX equipment and operators. The network reference model envisions a unified network architecture for supporting fixed, nomadic, and mobile deployments and is based on an IP service model.

The overall network may be logically divided into three parts: 1. Mobile Stations (MS) used by the end user to access the network. 2. The access service network (ASN), which comprises one or more base stations and one or more ASN gateways that form the radio access network at the edge. 3. Connectivity service network (CSN), which provides IP connectivity and all the IP core network functions.

The network reference model developed by the WiMAX Forum NWG defines a number of functional entities and interfaces between those entities. Fig below shows some of the more important functional entities. 1) Base station (BS): The BS is responsible for providing the air interface to the MS. Additional functions that may be part of the BS are micromobility management functions, such as handoff triggering and tunnel establishment, radio resource management, QoS policy enforcement, traffic classification, DHCP (Dynamic Host Control Protocol) proxy, key management, session management, and multicast group management.

2) Access service network gateway (ASN-GW): The ASN gateway typically acts as a layer 2 traffic aggregation point within an ASN. Additional functions that may be part of the ASN gateway include intra-ASN location management and paging, radio resource management and admission control, caching of subscriber profiles and encryption keys, establishment and management of mobility tunnel with base stations, QoS and policy enforcement, foreign agent functionality for mobile IP, and routing to the selected CSN.

3) Connectivity service network (CSN): The CSN provides connectivity to the Internet, ASP, other public networks, and corporate networks. The CSN is owned by the NSP and includes AAA servers that support authentication for the devices, users, and specific services. The CSN also provides per user policy management of QoS and security. The CSN is also responsible for IP address management, support for roaming between different NSPs, location management between ASNs, and mobility and roaming between ASNs.

Advanced Features of WiMAX
An important and very challenging function of the WiMAX system is the support of various advanced antenna techniques, which are essential to provide high spectral efficiency, capacity, system performance, and reliability. Two Type of Services: WiMAX can provide two forms of wireless service: 1) Non-line-of-sight: service is a WiFi sort of service. Here a small antenna on your computer connects to the WiMAX tower. In this mode, WiMAX uses a lower frequency range -- 2 GHz to 11 GHz (similar to WiFi). 2) Line-of-sight: service, where a fixed dish antenna points straight at the WiMAX tower from a rooftop or pole. The line-of-sight connection is stronger and more stable, so it's able to send a lot of data with fewer errors. Line-of-sight transmissions use higher frequencies, with ranges reaching a possible 66 GHz.

Very high peak data rates: WiMAX is capable of supporting very high peak data rates. In fact, the peak PHY data rate can be as high as 74Mbps when operating using a 20MHz wide spectrum. More typically, using a 10MHz spectrum operating using TDD scheme with a 3:1 downlink-to-uplink ratio, the peak PHY data rate is about 25Mbps and 6.7Mbps for the downlink and the uplink, respectively.

Scalable bandwidth and data rate support: WiMAX has a scalable physical-layer architecture that allows for the data rate to scale easily with available channel bandwidth. For example, a WiMAX system may use 128, 512, or 1,048-bit FFTs (fast fourier transforms) based on whether the channel bandwidth is 1.25MHz, 5MHz, or 10MHz, respectively.

Quality-of-service support: The WiMAX MAC layer has a connection-oriented architecture that is designed to support a variety of applications, including voice and multimedia services. WiMAX system offers support for constant bit rate, variable bit rate, real-time, and non-real-time traffic flows, in addition to best-effort data traffic. WiMAX MAC is designed to support a large number of users, with multiple connections per terminal, each with its own QoS requirement.

Robust security: WiMAX supports strong encryption, using Advanced Encryption Standard (AES), and has a robust privacy and key-management protocol. The system also offers a very flexible authentication architecture based on Extensible Authentication Protocol (EAP), which allows for a variety of user credentials, including username/password, digital certificates, and smart cards. Support for mobility: The mobile WiMAX variant of the system has mechanisms to support secure seamless handovers for delay- tolerant full-mobility applications, such as VoIP.

EC6802 WIRELESS NETWORKS.

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