The International Dynamic Spectrum Access Networks (DySPAN) symposium has emerged as the preeminent event to gather international economists, engineers, network architects, researchers and academic scholars together to share cutting edge research on and demonstrations of emerging wireless technology. DySPAN has since 2005 had a major influence on policy and technology research and development in the United States, Europe and Asia. The following bullets summarizes my key takeaways from DySPAN 2011:
- Much focus was on TV White Spaces (TVWS). Studies on available TVWS channels in different regions was presented, and there seems to be a lot. The correctness of TVWS database estimations with different path loss models was presented by Ranveer Chandra from Microsoft by comparing with sensing results. None of the path models tested gave false positives, thought the accurateness of the path loss model is crucial for maximizing spectrum utilization. Furthermore, Victor Bahl from Microsoft also presented their TVWS network trials. Bahl stated that Microsoft and Google are enemies when it comes to search, but they are in bed together when it comes to TVWS because both want to provide connectivity to everyone to best extent possible. Overall, TVWS seems to be accepted by the DySPAN community.
- Douglas Sicker from FCC presented the Spectrum Dashboard which also can be considered a tool to find available spectrum bands in the US. He also emphasized the importance of internationalization and encouraged a global market for dynamic spectrum access. He sends the message to DySPAN to work on this issue.
- David Cleevely presented analysis of the value per MHz versus technology and concluded that unlicensed spectrum generates more value than licensed spectrum! Furthermore, he concludes that femtocells will revolutionize the mobile industry.
- Krishan Sabnani from Bell Labs talked about spectrum virtualization and that a spectrum server is the final thing. He wants to use practices from virtualization in data computing. Base stations can be virtualized and run in the cloud.
- Pierre De Vries presented a paper where he propose that operating rights should be articulated using transmission permissions and reception protections, defined probabilistically (the Three Ps). Such a policy would remove the zero tolerance of interference limit violation and ease the introduction of dynamic spectrum access.
- Martin Weiss presented a paper where he focuses on the importance for the emergent regulatory policies to explicitly consider the requirements of secondary users, which not has been done yet because the secondary users not exists in meaningful number nor does they have any clear application. Furthermore he proposes to address this by explicitly consider the impact of the spatiotemporal properties of spectrum holes on the use decision by potential secondary users.
- Mitola is worried about commercializing the white space databases since he doubts that we can trust the commercial sector?
- In a panel about business perspectives on dynamic spectrum access, the urge of testbeds on white spaces was stressed by many. From an operators perspective Berna Sayrac from France Telecom mention that cognitive radio is much more than dynamic and opportunistic spectrum access, but that it can be used to manage our spectrum more efficiently. From a vendor perspective Lasse Wieweg from Ericsson mention that the most important for them is economy of scale, hence spectrum should be harmonized and he would like to see regulators worldwide to agree with each other and coordinate. He also states: do not be afraid of the higher bands such as 3.5 and 4.2 GHz.
The Internet Engineering Task Force (IETF) has recently initiated a standardization effort to standardize a Protocol to Access White Space databases (PAWS). The TV white space band is maybe the only relevant white space band at the moment, but it should be noted that this protocol addresses white spaces in general and can therefore be used for any band. This is an interesting standardization effort for future secondary spectrum access in various bands and also for the commercial progress of cognitive radio.
In more detail, the protocol will explore the various aspects of specifying a messaging interface between white space devices and the white space database. The protocol will also consider that multiple databases exist which contains information available channels at different locations.
Some days ago, FCC designated nine TV White Space database managers. These are:
- Frequency Finder
- KB Enterprises and LS Telcom
- Key Bridge Global LLC
- Spectrum Bridge
- Telcordia Technologies
- WSdb LLC
All companies have submitted proposal to be selected as a database administrator and all are selected for a period of 5 years if they succeed in implementing and testing the database. A trial of 45 days should also be successful prior to commercial launch of the database. Progressively, workshops that address the operation of the databases to ensure consistency and compliance with the rules and the database trials, are planned as soon as March 10, 2011.
Interestingly, FCC also explicitly states in the report that “… the Commission is also considering employing similar database approaches in other spectrum bands.”
The first cognitive radio standard IEEE 802.22 that started standardization in 2004 approaches its final release after some years of standardization. Why is it going so slow recently and why is there no push from the industry, or are these statements wrong? Is “fixed broadband in rural areas based on cognitive radio” not that attractive to most operators, hence no massive push from the manufacturers to develop equipment. Is the business case for fixed broadband in rural areas really positive when considering the risk of using access technology based on cognitive radio. Does there exist any initiatives to build an ecosystem around IEEE 802.22? In total, maybe cognitive radio is too immature and uncertain for the industry to make investments. However, it would certainly be interesting to see a realistic business case for IEEE 802.22.
Another standard which emerges is IEEE 802.11af, which will provide services similar to the traditional IEEE 802.11 standard, also known as WiFi when certified by the WiFi alliance. The main difference from the well known IEEE 802.11a/b/g standards is that IEEE802.11af will be a based on cognitive radio for operation in the TV White Spaces, that is the spectrum already allocated to the TV broadcasters and at the same time not used. No big investments are necessarily required in order to install and use a WiFi access point which actually can be done by everyone. The only prerequisite, when the regulatory rules are in place such as in the US, is the need for an incumbent database that maintains data about used frequencies in the TV band. Google has already announced that hey want to operate such a database. Rumors also say that WiFi alliance will certify IEEE 802.11af, which then will be WiFi, just based on cognitive radio.
The WiFi alliance which certifies WiFi products will be important for the success of IEEE 802.11af. In contrary, to my best knowledge, no such forums or alliance exist for IEEE 802.22. Maybe WiFi alliance could be the success factor required for the first commercialization of a cognitive radio technology in the TV white spaces, namely IEEE 802.11af. Also, rumors say that IEEE 802.11af only considers the minimum required cognitive functions for the first certified product, thus focus is on getting the standard released ASAP and then get products certified before FCC withdraws the rules. For later releases, more advanced functions could be introduced. This is similar to the IEEE 802.11b/g/n story.
In summary, maybe IEEE 802.11af will be seen commercially before IEEE 802.22 due to the speed of standardization and the ecosystem inherited from the WiFi alliance, even though IEEE 802.22 have existed for many years now. However, IEEE 802.22 should not be left out as it could be more attractive to general mobile networks if the use case and services offered are changed. For example, smaller cells such as micro-, pico- or femto-cells. Also mobility could be included. This would not be the most difficult change I guess. In fact, IEEE 802.22 would then be similar to WiMAX and LTE but with cognitive radio functions and opportunistic access. Such use cases and services could provoke more interests among the industry. Consequently, maybe an alliance or forum could be established for IEEE 802.22, or maybe the total IEEE 802.22 or the main cognitive functions could be adapted by the WiMAX Forum!