January 24, 2006
Technology in Focus features analysis of recent technology news articles, by the consultants in Technology Group, IDA. This is the top pick of the month from a list of 10-20 news analysis compiled monthly.
Nortel, Option Demo HSDPA at 3.6 Mbps, Electronic Engineering Times, 27 Dec 05
by Toh Bee Eng, Senior Consultant, Network Technologies
HSDPA represents the first step of WCDMA evolved. HSDPA moves key processing from the radio network controller to Node B and results in greater system throughput and improved quality-of-service result as the processing has moved closer to the air interface. HSDPA product launches, demonstration, suppliers and operators demonstrating the reality of a technology have indeed showing evident that the technology is capable of delivering to consumer with high speed, reliable, cost efficient data services.
Although HSDPA can coexist on the same networks with legacy WCDMA system and allows an operator to upgrade incrementally, minimizing upfront infrastructure investment for improvements that can cut the cost per bit of service delivery, the fact is that this technology has presented challenges for handset design. HSDPA is an upgrade only to the operator's downlink capabilities. For now, design changes include only the receive side of the handset. The transmit side, the W-CDMA uplink, essentially remains the same till in near future, when we see deployment of the High-Speed Uplink Packet Access (HSDPA) augmentation.
Since HSDPA builds on the 3GPP specification, handset designers can reuse much of their existing design work to develop HSDPA devices, though the handset will require higher performance signal-processing. HSDPA devices that come early to market are generally based on CDMA rake receiver technology. While rake receivers work well for conventional WCDMA, it can supports HSDPA to up to a few megabits per second only like those claimed by recent releases such as the 3.6Mbps reported in the above EE Times article. To achieve peak download speeds of 14.4Mbps, much advance equalizers design in the receiver and a dual-antenna system with receiver diversity are required.
Single antenna system is suitable for some implementations but it can only support full data speed capability when air conditions are optimal, hence dual-antenna systems with receiver diversity are favoured for high performance handsets. Although both antennas attempt to capture the same signal, designing receive diversity into the handset creates the best chance for good, clear reception. Each antenna operates on a signal transmission path independent of the other. The system then combines dual inputs to create the best possible signal. The advanced receiver design with dual-antenna system allows the handset to achieve higher download speeds for most air interface conditions but all of these increase design complexity and require additional circuitry and hence bigger size of the handset.
Some words about the writer
Toh Bee Eng joins IDA, the Technology Office as a consultant in Oct 2000 where she was working in the area of Cellular Network Technologies. She is currently holding a position as a Senior Consultant and her job duties include technology exploitation, provide consultation, to run technical trial projects with industry partners and to create awareness of new technologies available through discussions and giving presentations.
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