The rise and rise of HSPA

HSPA is on a roll. According to figures supplied by market research firm Wireless Intelligence, there were 245 HSPA networks in commercial service worldwide as of mid-May 2009. Moreover, a further 113 HSPA networks are in the process of being  deployed, trialled or planned.

True, the majority of HSPA networks in commercial service operate at the lower end of the throughput performance scale. (The Global Mobile Suppliers Association (GSA) says that, of today’s active HSPA networks, more than 70 per cent are restricted to 3.6Mbps peak downlink rates-the bulk of the remainder offer 7.2Mbps peak.) But the vendor community is not standing still.

“Today’s HSPA networks are capable of peak bit-rates of 14.4Mbps,” says Hans Beijner, a product portfolio manager at Ericsson. “The first networks using 64QAM modulation, giving 21Mbps, are also in operation.”

The use of higher order modulation schemes (from 16QAM up to 64QAM), along with MIMO technology, takes HSPA into ‘HSPA+’ territory. HSPA+ comes courtesy of 3GPP Release 7.

“Later this summer we will see the first commercial networks using MIMO supporting 28Mbps, and that will be followed quickly by the first networks supporting 42Mbps, using multi-carrier as described in Release 8 of 3GPP,” continues Beijner. “Next year we will see further enhancements to HSPA, utilising multi-carrier with MIMO and 64QAM modulation, which enables bit-rates of 84Mbps. This is part of Release 9 but further enhancements will come in Release 10 where it will be possible to use MIMO and 64QAM on four carriers, which will enable [peak] downlink bit-rates of 168Mbps.”

Developments are also moving apace on the latency and uplink fronts. Beijner again: “The first steps are being taken to reduce the TTI [transmission time interval] from 10ms down to 2ms, which would enable uplink rates of 5.8Mbps and a reduction in latency from today’s 50-60ms to 25-30ms,” he says. “The next step for the uplink is the introduction of 16QAM modulation, which will double the uplink bit-rate to 11.6Mbps. The combination of 16QAM modulation and multi carrier [Release 9] will give uplink bit-rates of 23.2Mbps in the 2010 timeframe.”

Despite the dazzling HSPA+ roadmap laid out by 3GPP network suppliers, only a handful of mobile operators have launched a commercial 21Mbps network or have it in trial. Telstra in Australia is the HSPA+ trailblazer with commercial operations already underway, while CSL in Hong Kong (a Telstra subsidiary) is among the few operators that are trialling 21Mbps HSPA+.

The GSA reports that many of today’s 3.6Mbps and 7.2Mbps HSPA operators are evolving to HSUPA, which requires ‘only’ a software upgrade: HSUPA provides an uplink peak of 5.8Mbps (as well as 14.4Mbps on the downlink). But 3GPP operators will have to think very carefully whether or not they want (or need) to go the full HSPA+ hog, or just simply wait until LTE arrives. HSPA+, using MIMO, requires additional base station hardware in the shape of antennas, which means extra capex-that could upset the business case for near- to mid-term HSPA+ deployment.

So where does all this leave WiMAX, a nascent fixed and mobile broadband technology looking to spoil the 3GPP party? Supporters of the 802.16e standard repeatedly claim that with peak downlink data rates of 40Mbps and peak uplink speeds of 10Mbps, it easily outstrips current HSPA performance.

Chris Pearson, president of 3G Americas, a 3GPP operator lobby group, believes HSPA+ deployments will cast a long shadow over WiMAX. When telecoms.com asked Pearson to assess the market threat of Clearwire, the flagship mobile WiMAX operator in the US, he unequivocally rejected the notion, often put forward by WIMAX supporters, that Clearwire-and other mobile WIMAX operators like it-should be seen as ‘complementary’ to 3G and ‘3.5G’ on the grounds that HSPA simply can’t match the data performance of WIMAX. 3G, say WiMAX supporters, is for nationwide voice and ‘narrowband’ mobile data, but 802.16e offers ‘true’ mobile broadband and a much better mobile internet experience.

Not so, says Pearson. “3G Americas and some independent technical research analysts have studied the performance metrics of WiMAX versus HSPA and HSPA+, and WiMAX has technical performance characteristics that are similar to HSPA and HSPA+,” he says. “Mobile WiMAX is not necessarily complementary to HSPA as HSPA is currently providing typical throughput speeds of 700-1700Kbps for downloads and 500-1200Kbps for uploads.”

That still means that current HSPA network performance is a little bit behind that of Clearwire, since the US WiMAX operator offers a typical downlink data speed of somewhere between 2Mbps and 4Mbps. But Pearson believes the HSPA roadmap will put WiMAX in the shade. “Typical peak user rates for HSPA+ have the possibility of reaching 5Mbps on the downlink and 3Mbps on the uplink,” he says.

But the fight for subscribers between WiMAX and HSPA will not just be fought on the battleground of throughput performance. Network coverage and device variety, says Pearson, will also be key market differentiators. “All major cities in the US currently offer HSPA coverage versus the two major cities with mobile WiMAX,” he says. “Sprint Nextel’s dual-mode WiMAX-EV-DO devices will help the Clearwire service offering a bit, as it fills the tremendous coverage challenges that WiMAX is currently having in the US. However, HSPA is clearly being chosen by mobile broadband customers throughout the US, as shown by the tremendous subscriber gains made by T-Mobile USA and AT&T Mobility during 2008.”

According to Wireless Intelligence, there were over 122 million active HSPA connections worldwide as of mid-May 2009. The market research firm predicts that by end Q209 there will be nearly 149 million HSPA users in total, up from nearly 59 million by end Q208. Wireless Intelligence further reports that there are now over 1,350 HSPAenabled devices on the market from over 130 different suppliers. WiMAX, on the other hand, has fewer than 100 devices to its name. And with AT&T having signalled its intention to spend $11bn this year on upgrading its current 7.2Mbps networks to HSPA+ (21Mbps), it looks like Clearwire and the WiMAX camp will come under even more competitive pressure.

For Intel, the US chip giant that has put billions of dollars behind WiMAX, the ‘HSPA versus WIMAX’ debate has been skewed by too much talk of headline data rates. “The peak data rates [the 3GPP camp] claim are exactly that,” says Siavash Alamouti, CTO of Intel’s Mobile Wireless Group. “Translate them to average capacity and you have significantly less capacity than you have with an OFDM system using MIMO. If HSPA had the same performance as WiMAX or LTE, we would not need these OFDM/MIMO technologies.”

As mobile WiMAX Release 1.0 (802.16e) is capable of 40Mbps peak downlink data rates, and peak uplink data rates of 10Mbps, Alamouti sees no meaningful competitive challenge to today’s mobile WiMAX networks in terms of typical, real-life performance. At the WiMAX Congress Asia 2009 event held in Singapore in April, the ‘better than cellular’ argument was heard loud and clear.

“Performance is the big differentiator and key for subscriber acquisition,” said Michael Lai, CEO of Malaysian operator Packet One (P1), which launched a commercial WIMAX service in August 2008. P1 claims it is achieving typical downlink speeds of between 5Mbps and 6Mbps compared to the sub-2Mbps level offered by Malaysia’s mobile operators. “In our demonstration at service launch, our WiMAX service far exceeded the performance of 3.5G, achieving up to 10Mbps on the downlink and 3Mbps on the uplink,” declared Peter Yen, president of Tatung Infocomm, a WIMAX operator in Taiwan. “3.5G typically offers 2Mbps on the downlink and 1Mbps on the uplink.”

Yen is confident that WIMAX will provide the network platform to propel Tatung Infocomm into a ‘full service digital provider’- which includes offering TV services-and compete head-on against the island’s cable and DSL providers, as well as 3G. The argument here, of course, is that because WiMAX can offer fixed, portable and mobile services over a single network, the business case for deployment is much more attractive than having to roll out different networks to serve different markets: 3G for mobile; DSL or fibre for fixed; and wifi hotspots for faster portable services.

“HSPA comes from the cellular model, while WiMAX is about the consumer electronics and internet model,” adds Intel’s Alamouti. “If you look at the protocol stack for WiMAX, you see Layer 1 and Layer 2 followed by IP on all the nodes. In 3GPP, you have legacy circuit switched elements, which were inserted into the protocol stack as a compromise between telephony-driven and IP-friendly companies. HSPA is more for smartphone-like applications and will not be able to meet the demands of bandwidth-rich devices, such as PCs, MIDs and netbooks. These devices will put a lot of strain on HSPA networks.”

Aside from the extra capacity WiMAX has, due to having what it claims as much better spectral efficiency than 3G, as well as wider channels-10MHz as opposed to the 5MHz channels used by 3G operators-802.16e Release 1.0 also lays claim to a much superior RAN latency performance according to data provide by Intel: 40ms latency for 802.16e compared with the 50-250ms for both HSPA and HSUPA. (It is worth noting, however, that Ericsson’s Beijner disputes Intel’s latency calculations, pointing out that they don’t take into consideration a shorter TTI. He says the correct latency figure for the 5.8Mbps uplink on HSUPA is 25-30ms.)

Alamouti also argues the cellular business model falls well short of WiMAX in terms of matching the lower opex costs that an all-IP flat architecture brings. “3GPP networks have still got to support legacy protocols, and are generally more complex, which make it less internet friendly,” he continues. For some analysts, however, the technical  and business case advantages that WiMAX might have over 3G are becoming increasingly irrelevant in light of commercial developments. “Yes, WiMAX backers are right to point out that mobile WiMAX has some technical advantages over existing mobile broadband systems, but EV-DO and HSPA backers are also right to point to their massive scale advantages over mobile WiMAX,” says Mike Roberts, principal analyst at Informa Telecoms & Media. “For example, HSPA and EV-DO together had more than 180 million subscribers worldwide at end-2008, compared to fewer than one million for mobile WiMAX  [out of a 3.6 million total of WiMAX subscribers].

This translates into cost advantages that mobile WiMAX will struggle to overcome.” Roberts continues: “Commercial results are what really matter and the early signs are not good for mobile WiMAX when it has gone head-to-head with HSPA and EV-DO. In four key markets with relatively large WiMAX launches- Korea, Australia, Malaysia and the US-WiMAX has only managed to gain two per cent of the total mobile broadband market, compared to 58 per cent for EV-DO and 41 per cent for HSPA.”

There are some caveats to these figures, as Roberts points out, in that the comparison is not conclusive given the different launch dates and the different characteristics of each technology. “But even more direct comparisons do not favour WiMAX,” adds Roberts.

“In Korea, WiMAX is comparable to HSDPA since the services launched within a quarter of each other in 2006 and are both focused on supporting mobile broadband data services.

But at end-2008 there were 8.4 million HSPA subscribers in Korea, compared to around 350,000 WiMAX subscribers.”

But Dr. Hyun-Pyo Kim, director of the WiBro Business Unit at KT, points out that most of the new HSDPA subscribers in Korea come from current 2G and 3G users who have been tempted to upgrade to new devices by high subsidies. “There’s not much change in the total number of mobile voice subscribers and pure market growth is negligible,” says Dr. Kim. “The mobile broadband data market, however, is a totally different story. This is a newly emerging market and most of the WiBro subscribers are new data service users who didn’t switch from other alternate services.

The increase of WiBro subscribers implies almost pure and new market growth.” The WiMAX camp also vehemently argues that, because of a distributed IPR regime, it can get non-subsidised WiMAX data cards and dongles out into market at much cheaper retail prices than 3G, whose IPR arrangements are dominated by Qualcomm. UQ Communications, a 2.5GHz licence holder in Japan, is currently conducting WiMAX service trials for free, provided users stump up the cost of the dongle or data card, which retail for $130 and $140 respectively. UQ claims that the cost of a typical 3G data card, when customers don’t sign up to a long-term contract, is $350. The non-subsidised device business model is something WiMAX sees as a key advantage over 3G. Dan Warren, director of technology at the GSM Association, suggests that the greater scale of the 3G market allows it to absorb the device subsidies, which, in turn, attracts more subscribers. “It doesn’t matter how much [the factory cost] of WiMAX devices undercut 3G, the price paid by the consumer is the one that counts,” he says.

Warren also questions the value of what the 802.16e customer gets for his data card money, particularly as WiMAX network coverage is limited. “The WiMAX data card is a Noddy device,” he says. “It doesn’t do a great deal for you if there is no fallback in terms of coverage. There are well over 100 countries where HSPA networks are deployed, and even where there is no HSPA coverage there is backwards compatibility [using HSPA devices] to pre-existing networks [GSM and WCDMA] with a roaming infrastructure already in place.”

Another bone of contention between WIMAX and 3G is the backhaul. Dr Teddy Huang, president CEO of Vmax, a WiMAX licensee in northern Taiwan, believes the more attractive WIMAX backhaul economics-compared with 3G-will be a key factor in offering a better performing and more cost-efficient service than cellular competitors. “3G operators use expensive TDM approaches with E1 [2Mbps] lines costing around NT$7,000 ($210) to NT$8,000 ($240) per month,” he says. “With WiMAX, we can use metro ethernet solutions that cost just a little more than NT$10,000 ($300) per month for 10Mbps capacity.”

This argument is given short shrift by Ericsson. “Even though most 2G and 3G networks today use TDM-based backhaul solutions, more and more operators are upgrading backhaul to IP-based fibre or microwave transmission,” says Beijner. “It is not correct to say that 3G is inherently ‘TDM-based’ as the change to IP transmission involves in most cases only a change of a transmission card in the base station.”

While the technical and business case arguments between HSPA and WiMAX are ongoing behind the scenes, the majority of mobile operators appear to have already made up their mind.

Only a major mobile WiMAX success story, in the shape of a Clearwire or a UQ, would force a radical reassessment of 802.16e’s role in the mobile broadband space. In the meantime, the HSPA juggernaut looks unstoppable.

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