There was IEEE WCNC 2012 conference in Paris from 1st to 4th of April. The hot issue during the conference was how to provide 1000 times more capacity. There seemed a consensus on general approaches to solve this challenge: higher network efficiency (CoMP/ICIC) for a given amount of spectrum/infra resource, more spectrum (sharing ‘good’ frequency band or utilizing higher frequency band), more infrastructure (small cell deployment in hetnet or densificiation).
During the conference, these were reflected in different ways. I attended a tutorial on the network interference coordination by Dr. David Gesbert. Even though interference coordination itself has been one of classical but challenging problems in wireless systems and addressed in many different ways. Nowadays, this is viewed as a more dynamic coordination problem for higher and higher network efficiency. Thus, two key requirements should be necessarily resolved in the future system: 1) accurate channel estimation on ‘multiple’ links and 2) sharing them among BSs ‘on time’. The former may not be feasible now due to the limited capability of current estimators in devices. On the other hand, the latter can be easily solved at the expenses of extra infrastructure. Then, research question seems obvious: can network efficiency increase compensate the extra infrastructure cost?
Spectrum sharing and small cell issues were discussed during two parallel panel talks: ‘The Role of Shared Use in Solving the (Projected) Spectrum Crunch’ and ‘Small Cells: A Smart Way towards Future Mobile Broadband’. It was interesting to me that people started open discussion on the spectrum sharing including licensed spectrum sharing where operators have equal right on shared spectrum which have been relatively overlooked in the academia. One of panels with economic background mentioned on the ‘cost’ of sharing spectrum, e.g., threat on service reliability. He also stressed out that the opportunity or threat of spectrum sharing all depends on operators’ individual situations, e.g., market positions or target services. As a panel from EU regulators pointed out, the operator-wise spectrum sharing may not be beneficial when operators have similar target customers in the same geographical areas. In research perspective, we relatively ignored equal-right sharing while we stick too much prioritized sharing, i.e., cognitive radio scenario although what actually are happening is mostly equal-right sharing, e.g., 3G network sharing or WiFi deployment in unlicensed band.
Meanwhile, small cell issues were mainly discussed in the context of the low power nodes, i.e., femto or pico cells, rather than desificiations of existing macrocells. Thus, most of panels were from the small cell vendors targeting potential femtocell markets rather than big cellular vendors. Still, such small cell vendors eager to find the business model and an eco-system for collaboration with existing big vendors since WiFi solutions are now good enough in terms of cost and offloading capability. A key research question is up to how much traffic can be cost-effectively managed by WiFi which inherently lacks inter-cell coordination due to CSMA/CA protocol. There was an interesting traffic demand projection in the next two years shown by Dr. Alamouti (currently Group R&D Director in Vodafone). Vodafone’s prediction on traffic burden on cellular networks may not be doubled in next two years. Rather, 20~30% increase would be more realistic since they assume that WiFi will work well to offload the potential demand. However, this would be true only when WiFi manage well more than doubled capacity. It could be or not.