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Just as operators and vendors are continuing to enhance HSPA even with LTE on the horizon, so they are still finding a strong place for the 2G+ technology EDGE, and combining with this system will be a major opportunity for WiMAX. One of the most important markets for Mobile WiMAX will be as an overlay for GSM/EDGE operators looking to offer broadband to selected user bases without the cost and risk of a wide area 3G build-out. Addressing this, several vendors showed WiMAX/EDGE combinations at Mobile World Congress endorsing a view that to date has largely been driven by start-up Comsys of Israel, and Nortel, which was particularly aggressive about EDGE Evolution systems.
In its transition from a model driven by system IP to a baseband processor business, Comsys has majored on the WiMAX/2G combination for handsets, which it sees as the earliest opportunity for 802.16e among cellcos. As larger players start to take the same view, Comsys claims a headstart of at least a year. At MWC it added the CM1265 to its ComMAX line, including WLan alongside WiMAX and GSM/EDGE. This joins the CM1100 full mobile WiMAX baseband processor and the CM1125 integrated multimode GSM/WiMAX baseband. The new device will support Mobile WiMAX Release 1.x TDD and FDD profiles, and integrate GSM/EDGE and 802.11b/g/n, including support for seamless service continuity.
Meanwhile, both NXP and Samsung jumped on the WiMAX/EDGE train. Alcatel-Lucent showed the Samsung devices, offering service continuity across WiMAX and GSM-EDGE networks. Samsung was already a partner in Alcatel-Lucent’s Open CPE Program for WiMAX, and the French vendor’s VP of WiMAX, Karim El Naggar, said: ‘Wireless operators will be able to offer truly ubiquitous mobile data experience even before WiMAX is fully deployed nationwide. Instead of having to invest upfront in a massive roll-out, wireless operators will be able to offer superior service in the dense urban environments covered by initial WiMAX deployments, while relying on GSM/EDGE nationwide availability from day one and gradually extend WiMAX coverage nationwide.”
NXP announced a Dual-Mode EDGE-WiMAX Reference Design using its own Nexperia 5210 cellular product and Intel’s Baxter Peak WiMAX chip for ultramobile PCs, officially called WiMAX Connection 2400. A fully validated reference design will be available from NXP in the second half of this year.
Looking further ahead, Nortel put its weight behind the next iteration of EDGE, which has previously been pushed mainly by Ericsson. Evolved EDGE is a multichannel, packet-based technology that merges several 40KHz channels to increase capacity. According to Nortel, it behaves similarly to UMTS at the cell edge and requires only a software upgrade to the base station. However, it has yet to achieve a crucial milestone: the support of a handset major.
Ericsson says it will launch commercial EDGE Evolution products by the start of 2009, making a vocal commitment to this technology as one with a long term future. The Swedish giant claims to supply the "majority" of all the 200 commercial EDGE networks in use around the world. It clearly sees the Evolution software upgrade as a further way to reap cash from the platform, building on its recent successes with GSM/GPRS in markets where 3G spectrum is not available or where operators are holding back from full scale mobile broadband. Nokia says the typical EDGE impact on monthly ARPU is an increase of around €1 compared to GPRS, or 10-40% higher data ARPU. Similar gains are also possible with EDGE Evolution, even in markets with competitive pricing.
EDGE works by improving the signaling interface to deliver on average three times the performance of GPRS, with the current release providing and average data rate of 80-160Kbps per user in mobile terminals supporting 2-4 timeslots.
The main improvements promised by Evolution Release 7 include:
• faster and better cell reselections with NACC/NCCR
• guaranteed bit rates with streaming quality of service (Enhanced QoS)
• enhanced service continuity with W-CDMA/HSPA.
• enhanced data rate through lower latency and other techniques.
• dual carriers in the downlink, increasing the carrier bandwidth available above 200KHz. Today’s EDGE terminals receive signals on up to five timeslots, but the introduction of dual carriers doubles the available bandwidth (to 40KHz) as well as the practical peak bit rate. Using dual carriers and five timeslots on each carrier provides bit rates of almost 600Kbps with no other changes to EDGE.
• higher average and peak bit rates and improved spectral efficiency are achieved through more advanced modulation, using 16QAM instead of 8-PSK for some schemes; more efficient channel coding for better error correction; and an increased symbol rate (in practice, increasing the carrier bandwidth). All this boosts peak bit rate to 100Kbps per timeslot, equating to user bit rates of 1Mbps if dual carriers are used.
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