Coming to a fork in the road – will all paths lead to IMT-Advanced?

(May 14 2012)

1. “What is 4G wireless?” Ask this question of any five people you know in the mobile broadband industry. It’s highly probable that you’ll receive five very different answers. In fact, ask ten or even twenty people and the outcome is likely to be the same.

   The number of definitions of 4G wireless that exist today seems only to be limited by the number of opinions one seeks. Definitions might just include technologies such as HSPA, HSPA+, LTE, LTE Advanced and WiMAX. And in some cases the definition may even reference IMT-Advanced.

   "As the most advanced technologies currently defined for global wireless mobile broadband communications, IMT-Advanced is considered as '4G,' although it is recognized that this term, while undefined, may also be applied to the forerunners of these technologies, LTE and WiMAX, and to other evolved 3G technologies providing a substantial level of improvement in performance and capabilities with respect to the initial third generation systems now deployed," espoused the ITU in a PR released in December of 2010.

   The phrases ‘evolved 3G technologies’ and ‘substantial level of improvement’ in the ITU’s statement leave much open to interpretation. That interpretation has generated a fair amount of debate between specific technology proponents and it’s also been a big enabler of powerful new marketing campaigns by carriers.

   But pulling back the covers on the ITU’s technical specifications reveals the possibility that LTE Advanced, HSPA+ Advanced and WiMAX 2 all could be viable contributors to IMT-Advanced. Spectrum, spectral efficiency and latency are all key requirements of the definition and to one extent or another, can be addressed by these three technologies.

   So far, operators who have deployed LTE networks have done so using solutions based on Release 8 or Release 9 standards. Release 10 and Release 11 will deliver LTE-Advanced, as standardized by 3GPP. The first of these networks are appearing this year with broader implementations taking place by 2015.

   3GPP is developing the following capabilities for LTE-Advanced:

   Wider bandwidth support for up to 100 MHz via aggregation of 20 MHz blocksUplink MIMO (Two transmit antennas in the device)Downlink MIMO of up to 8 by 8Coordinated multipoint transmission (CoMP) with two proposed approaches: coordinated scheduling and/or beamforming, and joint processing/transmission.

   LTE-Advanced will be both backwards- and forwards-compatible with LTE, meaning LTE devices will operate in newer LTE-Advanced networks, and LTE-Advanced devices will operate in older LTE networks.

   AT&T, Sprint and T-Mobile have been the first North American operators who have discussed specific plans to rollout LTE-Advanced to implement carrier aggregation and to enhance the speeds of their existing LTE products.

   Krish Prabhu, CTO and president of AT&T Labs announced in late 2011 that AT&T is planning the deployment of an LTE-Advanced network in 2013. AT&T has yet to provide further details regarding timing or the nature of the network's upgrade. T-Mobile USA has also plans to launch LTE in the latter part of 2013. According to CTO, Neville Ray, T-Mobile USA plans to continue investing in its current HSPA+ network, while deploying LTE infrastructure that is Release 10 software capable of eventually supporting LTE-Advanced. He expects to see greater availability of equipment supporting LTE-Advanced and the benefits of carrier aggregation to begin to be seen in 2014.

   Sprint’s has announced plans for its initial LTE deployment limited to only a pair of 5 MHz carriers in its 1900 MHz spectrum band, in selected markets during 2012 with broader deployments in the first half of 2013. Sprint is also re-farming its existing 800 MHz iDEN spectrum allocations and will leverage LTE-Advanced to aggregate LTE capacity across these bands beginning in 2014. More recently Clearwire’s CTO, John Saw, announced plans to commercially launch its LTE-Advanced network in June 2013. According to Saw, Clearwire will begin with 20 MHz carriers and when carrier aggregation becomes commercially available sometime in 2014, and the operator will later move to 40 MHz, the maximum spectrum allocation specified in the IMT-Advanced requirements, in order to deliver theoretical peak speeds of up to 168 Mbps. It is likely that Sprint will also take advantage of Clearwire’s LTE-Advanced deployments to futher expand LTE capacity.

   Absent from the buzz of LTE-Advanced is Verizon. While the operator has deployed the most extensive LTE network with more than 8 million subscribers in the US, it has not yet offered up an announcement or plans to adopt LTE-Advanced. Verizon has established ‘4G LTE’ brand recognition with consumers using its current LTE offering, and has indicated that the next natural step in the company's data evolution chain will be LTE-Advanced. The question is not whether, but when, plans for the natural next-step will be announced.

   More than two million subscribers to NTT DOCOMO’s Xi® extra-high-speed LTE mobile service already experience a maximum downlink of 75 Mbps, and Japan’s leading mobile operator has been pre-licensed to conduct field experiments of LTE-Advanced. Once the formal license is issued, DOCOMO plans to begin field experiments of LTE-Advanced in real radio environments in the cities of Yokosuka and Sagamihara in Kanagawa Prefecture, Japan.

   At 4G World 2012 network operators, network builders and industry experts will examine the roadmap to IMT-Advanced for current operators of HSPA+, LTE and WiMAX networks. Delegates will learn first-hand, from those who know, about the opportunities and challenges of planning, building and operating true 4G networks. Join operators and equipment vendors for detailed insights into the technology that will deliver on the promise of 100 Mb/s, fully-mobile, all-IP networks.

   By:  Andy Mitchell, Editor, 4G Trends

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