Fourth-generation wireless technology (4G) was in the news this week as Samsung demonstrated 100 Mbps while moving in a bus. NTT DoCoMo, the giant Japanese-based telecommunications company and Korean-based Samsung are both testing 100 Mbit/s mobile technology. Samsung said it demonstrated 60 km/h multi-cell handover at 100Mbps. But practical considerations such as range, available spectrum, and bandwidth requirements have yet to be resolved.

NTT DoCoMo says it plans on releasing the first commercial network in 2010 while Samsung plans on commercialising the service by 2010 at Jeju Island, South Korea. The 3.9G or LTE (Long Term Evolution) approach, developed by the 3rd Generation Partnership Project (3GPP) brings together a number of telecommunications standards bodies to develop a follow-on to the “3G” standard.

Sprint last month announced that it will use Mobile WiMAX and called it “4G”. That term is normally applied to wireless networks with download speeds above 100 Mbps. But Mobile WiMAX could get there in a few years. Presently, Mobile WiMAX, using 10 MHz-wide channels in the 2.5 GHz band, delivers some 25Mbps. Individuals may get 2-4 Mbps down.

There are several approaches to “4G”.

• The 3GPP group:
  Today’s W-CDMA (3G) standard essentially comes to a standards halt after HSPA. GSM/UMTS/WCDMA vendors like Nokia, Ericsson, Lucent and Nortel first plan what Nokia calls 3.9G, or Super 3G. Known as UTRAN LTE, or Universal Terrestrial Radio Access Network Long Term Evolution, its peak data rates are targeted to reach up to 100 Mbps in the downlink and 50 Mbps in the uplink. The standard of 3.9G is to be finalized in 3GPP in mid 2007. Deployment of Super 3G might be expected by 2009-10.
• The 3GPP2 group:
  Backed by Qualcomm and friends, CDMA’s EVDO-Rev B adds multicarrier capability and 5 MHz channels instead of 1.25Mhz channel spacing currently used by EVDO-Rev A. Flarion’s attempt to turn Flash-OFDM into an IEEE standard, 802.20, was thwarted by Qualcomm a couple of years ago. Then Qualcomm bought the company. Currently, 802.20 has become mired in controversy and stalled by the IEEE over questions of Qualcomm dominance.
• Mobile WiMAX (IEEE 802.16e):
  WiMAX holds out the prospect of a globally harmonized, fixed and mobile network that could deliver 4G performance – as defined above - before the end of the decade. Already companies like Motorola and Siemens are demonstrating OFDM networks at close to 1Gbps, while others are showing off connections at high speed, up to 100 kilometers per hour.

The technology behind NTT DoCoMo’s 4G uses a method called Variable-Spreading-Factor Spread Orthogonal Frequency Division Multiplexing (VSF-Spread OFDM), which increases downlink speeds by using multiple radio frequencies to send the same data stream. MIMO is used to enable a cellphone to receive data from more than one base station in range. Four antennas, each sending 250Mbit/s streams of data, was used by DoCoMo.

In May 2003 NTT DoCoMo carried out a field trial of a fourth-generation (4G) mobile communications system in Yokosuka, Kanagawa Prefecture, near the main DoCoMo R&D centre. The trial was conducted to aid in the development of a 4G ‘packet wireless transmission system’ global standard, which is currently under discussion by the International Telecommunication Union’s Radiocommunication Sector (ITU-R).

VSF-OFCDM enables downlink connections of extremely high speeds, both indoors and outdoors, while VSF-CDMA realises high-speed, high-efficiency packet transmissions for the uplink. Four MIMO antennas combined with 16 QAM data modulation and turbo coding speed things up, but cost more and consume more power.

Implementing the 100-MHz and 40-MHz bandwidths in the downlink and uplink respectively may be the tricky bit. Where will the ITU find spare “4G” spectrum? If the ITU has to dedicate a new band, it might have to go up to 60 GHz (or beyond), for spectrum. That could limit range to a few blocks making it impractical for anything but urban cores.

MIMO is old hat to Nortel and Orthogon Systems.

Nortel demonstrated peak data rates of 37 Mbps over a standard 5MHz PCS mobility band, last year. It took into account the noise and fading conditions found on a real-world cellular network.

Orthogon Systems currently sells their OS-Spectra gear that delivers aggregate throughput of 300 Mbps on a 30 MHz channel. Four simultaneous signals are sent between pairs of transceivers at each end of a 5.4 GHz and 5.8 GHz link.

Other high speed research projects, mostly using MIMO, include:

• The evolving 802.11n standard, using MIMO antennas and wider bandwidths (40MHz) can hit speeds beyond 300Mbps. The “greenfield” 5.4 GHz WiFi band would have the least interference, but power is limited for WiFi. Range of unlicensed 802.11n might be a block or two. The Wi-Fi Alliance plans to begin certifying next-generation 802.11n products starting in 2007 in a two-phased approach to the 802.11n certification with final approval in 2008.
• Siemens demoed 1Gbps wireless connection in 2004. It used four MIMO antennas and 100 MHz bandwidths. Siemens, a partner in the WIGWAM project, projected a tenfold increase in data and multimedia transmissions by the time the next generation of wireless is expected in 2015.
• The Wireless Gigabit with Advanced Multimedia (WIGWAM) project is a German-led consortium of corporate and university researchers. The targeted spectrum is the 5 GHz band with the extension bands 17, 24, and 60 GHz with scalable data rates. It is using the 108Mbps 802.11n and MIMO technology as the starting point for bringing 1Gbps wireless into offices and homes.
• MIT’s WiGLAN project is researching circuit designs allowing a 1Gbps wireless network using the 5.8GHz band. The MIT effort would create a small WiGLAN adapter connecting video streams, digital cameras, printers and mobile devices to the Internet. The adapter provides a 150MHz bandwidth using the 5.8GHz band.
• OGRE (On-silicon Gigahertz Radio Exploration) focuses on the 7GHz of unlicensed spectrum available around the 60GHz band, an area key to WIGWAM and other wireless gigabit research. Researchers at the University of California are developing it.
• Extricom says their Wi-Fi switch/AP triples the bandwidth of 802.11a/g to more than 1Gbps.
• NewLANs is still promising 2Gbps to the desktop. Although NewLANs is active in the UWB community, the company’s Web site remains blank.
• MILTON (Microwave Light Organized Network), can have as many as 32 focused beam “petals”, each delivering some 50 Mbps, providing WiMax on the unlicensed 5.8 GHz band.

Related DailyWireless MIMO stories include; Finding MIMO, Jump to Light Speed, 3G World Conference, 60 Ghz Long Shot, Re-animating Backhaul, FCC Liberalizes 70-90 GHz, Gigabit WiFi, 60 GHz Radios, YDI Goes 24GHz, Dartmouth’s Triple Play, GigE to the Home - Wireless Next?, GigE WiMax? and More Gigabit Wireless.

Posted by Sam Churchill on Friday, September 1st, 2006 at 4:37 am.