Lucent Technologies Bell Labs Innovations 1 A Survey of Enabling Technologies for 3G+ Wireless Systems Vincent Lau Bell Labs, Lucent Technologies Dec 20, G???

Lucent Technologies Bell Labs Innovations 2 Outline  Background on Cellular Systems  Evolution of Cellular Systems  Advanced Technologies for 3G+ Systems –Physical Layer Enhancement: »Multiple Antenna Processing - BLAST »OFDM »Utilization of Feedback –MAC Layer Enhancement: »Adaptive Scheduling –Architectural Enhancement: »Information Hot-spot Architecture  Illustration with UMTS - HSDPA:

Lucent Technologies Bell Labs Innovations 3 Background of Cellular Systems  Key Components: –Mobile station, base station, switch. –Bottleneck is usually on the air interface due to the limitation on radio resource.  Radio Resource: –Power, Bandwidth

Lucent Technologies Bell Labs Innovations 4 Evolution of Cellular Systems  1G systems (AMPS, TACS) –Analog Transmission (FM). –Voice Applications only.  2G systems. (GSM, CDMA, IS54) –Digital Transmission. –Voice and Data applications (Circuit Switched only). –Cellular and PCS.  2.5G systems (GPRS/EDGE, 3G1X). –Digital Transmission, –Circuit Switched voice and data (same as 2G + medium speed) –Packet switched data (medium speed, No QoS). –Overlay Infrastructure with 2G Systems.

Lucent Technologies Bell Labs Innovations 5 GPRS Infrastructure  Voice Path - same infrastructure as GSM.  Data Path - via an overlay IP-based network of SGSN - GGSN.

Lucent Technologies Bell Labs Innovations 6 Evolution of Cellular Systems  3G systems. –Digital transmission, –Circuit switched voice and data (low speed) –Packet switched data services (high speed ~ 2Mbps, with QoS). –Integrated Core Network Infrastructure between voice and data paths.

Lucent Technologies Bell Labs Innovations 7 Post 3G Systems  3G+ Systems?? –Based on existing 3G spectrum (not new spectrum). –By 2010, 66% of the revenues will come from data services –UMTS - Release 99/4 systems alone will not be capable to meet these demands. (Realistic outdoor data rates will be limited to 384kbps). –Ultra high speed packet data service (10.8 Mbps) –All-IP Core Network.

Lucent Technologies Bell Labs Innovations 8 Advanced Technologies – Physical Layer Enhancement –Multiple Antenna (MIMO) Processing: »Traditionally, the speed of a wireless link is limited by the radio resource (power, bandwidth). »When the transmitter has antennas and the receiver has antennas, the link speed increases linearly with given the same power and bandwidth budget. »Multiple Antenna introduces Spatial Dimension into the radio resource set. »Similar to fixed line scenario except there are mutual interference between the spatial channels.

Lucent Technologies Bell Labs Innovations 9 Advanced Technologies – Physical Layer Enhancement  BLAST (Bell-Labs Layered Space-Time Architecture) –At the transmitter, n independent data streams are transmitted out of the n antennas on the same bandwidth. –At the receiver, each receive antenna "sees" all of the transmitted sub-streams superimposed, not separately. –If multipath scattering is sufficient, these n data streams have different spatial signatures to each of the n receive antennas and they are separable. –The processing involved is linear and could be (interference nulling or MMSE). –Lucent has produced the world’s first BLAST receiver chip for mobile device. –

Lucent Technologies Bell Labs Innovations 10 Advanced Technologies – Physical Layer Enhancement  Block Diagram

Lucent Technologies Bell Labs Innovations 11 Advanced Technologies – Physical Layer Enhancement  Orthogonal Frequency Division Modulation (OFDM) –Traditionally, transmission of a wideband signal is more difficult than a narrowband signal. –This is due to multi-path effects  Inter-symbol interference. –Complex equalizer is needed to overcome this effect. –OFDM is an effective technique to transmit wideband signal. –Serial input data is split into N parallel streams, each stream is fed into a “frequency channel”. –With respect to each data stream, it is a narrowband signal, and could get through the channel easily without equalizer. –At the receiver, the N parallel streams are combined.

Lucent Technologies Bell Labs Innovations 12 Advanced Technologies – Physical Layer Enhancement  Utilization of Feedback: –Wireless channel is time varying. {Good   Bad} –Adaptive transmission is possible to exploit the time varying nature of the channel. –High throughput transmission mode is employed when channel is good, –When channel is bad, low throughput transmission mode is employed for better protection. –Need the feedback of channel condition to the transmitter.

Lucent Technologies Bell Labs Innovations 13 Advanced Technologies – MAC Layer Enhancement  Jointly Adaptive MAC Scheduling: –For voice service, data source is quite steady. Optimal strategy is to power control users so as to act against fading  maintain a steady channel throughput. –For packet data service, data source is in burst. Optimal strategy is to act in line with fading. Increase power when channel is good. Decrease power when channel is bad. –For multi-user network, MAC layer is used to coordinate resource allocation among different users. –Between a user and a base station, the link throughput (speed) is adaptive based on the link condition. –The key is to have a jointly adaptive MAC layer and physical layer. –Priority is given to users with good channel conditions. (because they could use the radio resource more effectively).

Lucent Technologies Bell Labs Innovations 14 Advanced Technologies – MAC Layer Enhancement  Since users are independent with each other, we could always find users with good channel condition at any given time (if the total number of user is large)  Multiuser Diversity.  In addition to maximum network capacity, fairness is also an important attribute.

Lucent Technologies Bell Labs Innovations 15 Advanced Technologies – MAC layer Enhancement  Proportional fair is another common objective of scheduling.

Lucent Technologies Bell Labs Innovations 16 Advanced Technologies – Architectural Enhancement  Information Hot-spot Architecture (Wireless LAN vs Cellular Systems): –High speed, low mobility, localized-coverage wireless multimedia access --> hot spot access points. (e.g. Wireless LAN Access Point). –Medium speed, high mobility, macro-coverage --> cellular wireless. (e.g UMTS) –Mobility between localized hot-spots and cellular wireless through mobile-IP.  The WLAN advantages: –Order of magnitude higher data rates than 3G –Rapidly falling price (available from retail) –HW embedded in laptops (Dell, IBM, Toshiba, Fujitsu, Acer). SW supported in Window XP –50% of USA laptops and PDAs are expected to be WLAN- enabled by 2004.

Lucent Technologies Bell Labs Innovations 17 Information Hot-spot Architecture (Tight Integration)

Lucent Technologies Bell Labs Innovations 18 Information Hot-spot Architecture (Loose Integration)

Lucent Technologies Bell Labs Innovations 19 Mobile-IP Operation Traffic is sent as usual to the home subnet The home agent intercepts (Proxy ARP) the traffic while the mobile node is registered as away Traffic is tunneled to its current location Traffic from the mobile node can go directly to the correspondent host Mobile Node Home Agent Foreign Agent

Lucent Technologies Bell Labs Innovations 20 Wireless Virtual Private Network W-LAN Hot Spot Ethernet Internet Xedia AP1000 HA Corporate Network NavisRadius Home AAA Server Access Points Dual-mode terminal w/ MobileIP client Xedia FA NavisRadius Local AAA Server Mobile-IP tunnel Lucent PCF BS BSC BS PDSN Springtide (FA) WSP NavisRadius Local AAA Server End-to-end IPSec tunnel

Lucent Technologies Bell Labs Innovations 21 An Example of 3G+ Evolution - UMTS HSDPA (High Speed Downlink Packet Access) Release 99/4 DCH/DSCH 2 Mbps Packet Mar 00 Dec 00 R99 R4 Hybrid ARQ Dynamic Scheduling Dynamic Scheduling Adaptive Modulation & Coding Adaptive Modulation & Coding HSDPA Release 5 Enhanced Channel Structure Enhanced Channel Structure 2.4Mbps Packet June 02 HS-DSCH ‘03 Fast Cell Selection Fast Cell Selection MIMO HSDPA Release Mbps Packet (2x2) 20 Mbps Packet (4x4) HS-DSCH

Lucent Technologies Bell Labs Innovations 22 Practical considerations at the terminal  For uncorrelated fading, 1/2 lambda spacing is sufficient because of local scatterers.  Each antenna requires RF/IF chain. Significant cost savings using direct conversion (homodyne) solutions.  20% and 70% of baseband processing used by VBLAST detector and turbo decoder, respectively, for (4,4) receiver. Overall processing is within range of existing hardware technologies. Antennas used in MIMO channel measurements