Presentation on theme: "Wi-Gig Utilizing Unlicensed 60 GHz Spectrum. Usage Models Wireless Display Desktop storage and display Projection to TV or projector in conference room."— Presentation transcript:
Usage Models Wireless Display Desktop storage and display Projection to TV or projector in conference room or In-room gaming Streaming from camcorder to display Professional HDTV outside broadcast pickup Distribution of HDTV Video streaming around the home Intra-large-vehicle applications (e.g. airplane, ferry) Wireless networking for office Remote medical assistance Rapid upload/download Rapid file transfer/sync Picture-by-picture viewing Airplane docking (manifests, fuel, catering,..) Downloading movie content to mobile device Police surveillance data transfer
Replacement of Cable in the PAN 60 GHz millimeter wave transmission will scale the speed of WLANs and WPANs to 6.75 Gbit/s over distances less than 10 meters. This technology is the first of its kind and will eliminate the need for cable around personal computers, docking stations, and other consumer electronic devices. High- definition multimedia interface (HDMI), display port, USB 3.0, and peripheral component interconnect express (PCIE) 3.0 cables will all be eliminated. Fast downloads and uploads, wireless sync, and multi- gigabit-per-second WLANs will be possible over shorter distances.
60 GHz Link Budget primary challenge with millimeter wave operation is the much poorer path loss than in the microwave band. For example, the free space path loss at 1 m for 60 GHz is 68 dB compared to 47 dB at 5 GHz. Even attenuation due to person obstructing the path ranges between 10 – 15 dB We further compare a 60 GHz link budget to a 5 GHz 802.11n link budget, as follows. There is a 21 dB increase in path loss from 5 GHz to 60 GHz. In addition current technology for low cost consumer devices in 60 GHz will reduce transmit power in 60 GHz by 6 dB as compared to 5 GHz. Based on the channel bandwidth increase of 50x, the increase in noise bandwidth results in another 17 dB loss. And again current 60 GHz technology will initially result in 3 dB worse noise figure than 5 GHz technology.
However, the target applications and use cases are shorter range for this technology (leaning towards personal area networking), so 10 dB can be added to the link budget margin for 60 GHz compared to longer range 5 GHz system. In addition, typically 60 GHz system design will be target a lower order modulation than an 802.11n system due to the large channel bandwidth, which could result in a 5 dB gain. In summary there could be a 32 dB loss (or larger) in link margin from 5 GHz to 60 GHz.
Physical layer 802.11ad defines four different PHY layers: Control PHY, SC PHY, OFDM PHY and low-power SC PHY (LPSC PHY). Control PHY is MCS 0. SC starts at MCS 1 and ends at MCS 12; OFDM PHY starts at MCS 13 and ends at MCS 24; and LPSC starts at MCS 25 and ends at MCS 31. MCS 0 to MCS 4 are mandatory PHY MCSs. Here, we briefly describe the different PHYs and their packet structures. The system clock rate is 2640 MHz, and this rate is used for OFDM also. Control, SC and LPSC PHYs have a clock rate of 2/3 × 2640 = 1760 MHz common with all 802.11 packet formats, the packet consists of a short training sequence, a channel estimation sequence, the physical layer convergence procedure (PLCP) header, MAC packet, and cyclic redundancy check (CRC). Although there are different PHYs, they all have this unique structure, which ensures implementers do not need to change packet formats when using different PHYs. The only difference is that each PHY is a different size and uses a different Golay code.
MAC Layer The primary challenge for the 60 GHz MAC is how to handle directional transmissions used to mitigate the high propagation loss of millimeter waves. Prior to 802.11ad, the 802.11 MAC relies on Omni- directional transmissions for management and control frames (e.g. beacons, RTS/CTS) to ensure they can be heard by everyone in the BSS. With directionality, device discovery becomes more complicated. Furthermore, devices need to find the best direction for communication, which necessitates support for a beam forming protocol. Also the basic 802.11 concept of CSMA/CA has limitations in the presence of directional transmissions.
The 802.11ad super frame is called the beacon interval and comprises a beacon transmission interval (BTI), a data transfer interval (DTI), and optional association beam forming training (A-BFT) or announcement transmission intervals (ATI) The DTI can include one or more service periods (SPs) and contention-based access periods (CBAPs).
Combating High Path Loss Beam forming Protocol Because of the highly directional nature of 60 GHz communications, the transmitter and receiver antennas need to be aligned in the right direction to obtain maximum gain. 802.11ad supports up to four transmitter antennas, four receiver antennas, and 128 sectors. Beam forming is mandatory in 802.11ad, and both transmitter-side and receiver-side beam forming are supported.
Backward compatibility with existing 802.11 standards Fast session transfer (FST) protocol allows different streams or sessions to transfer smoothly from one channel to another in the same band or different bands. This protocol makes 802.11ad compatible with the forthcoming 802.11ac standard and other existing standards, such as 802.11a/b/g/n. The protocol allows different radios in the same device to operate simultaneously or not simultaneously. Devices with 802.11ac and 802.11ad can have same MAC address or different MAC addresses. If the same MAC address is used for all the radios in different bands then FST is in transparent mode. If the MAC addresses differ according to channel/band, then FST is not transparent.
Fast Session Transfer Protocol Fast session transfer (FST) protocol allows different streams or sessions to transfer smoothly from one channel to another in the same band or different bands. This protocol makes802.11ad compatible with the forthcoming 802.11ac standard and other existing standards, such as 802.11a/b/g/n. The protocol allows different radios in the same device to operate simultaneously or not simultaneously. Devices with 802.11ac and 802.11ad can have same MAC address or different MAC addresses. If the same MAC address is used for all the radios in different bands then FST is in transparent mode. If the MAC addresses differ according to channel/band, then FST is not transparent.
Conclusion Wi-Fi products based on next generation gigabit per second 802.11 technology will be emerging on the market soon to address use cases that demand higher throughput. 802.11ac will evolve in the 5 GHz bands with wider channels and multi-user capability to address broader coverage use cases typical of Wi-Fi devices, such as higher resolution video coverage around the home. 802.11ad will address personal area networking use cases new to 802.11 such as wireless docking with multi-gigabit per second links based on large amount of available spectrum in the 60 GHz band. 802.11ad will make use of directional antennas and beamforming to enhance link quality, and modifies channel access to address directionality and spatial reuse.