Radio Resource Allocation for Multi User Spectrum Sharing with Parameter Uncertainty

Spectrum sharing (SpS) technology has continued to develop since its introduction as an alternative spectrum management policy by the US's Federal Communication Commission (FCC) in 2002. Radio resource allocation (RRA) is a crucial function in SpS technology which allocates the available radio spectrum to the secondary users and adjusts the transmission parameters such as secondary user transmit power and rate in an efficient way so that the system performance is maximised. RRM is implemented in the secondary network and needs to address the following significant technical challenges. Input parameters to RRA algorithms include spectrum availability and channel gains. Spectrum availability is evaluated using a spectrum sensing mechanism with a certain level of accuracy. The required channel gains are also evaluated using signal processing techniques with a given level of estimation errors. One of the main challenges is that in most cases there is either no or very limited signalling between the primary and secondary networks. This makes parameter estimation a very complicated task with a limited level of accuracy, particularly for those parameters which needed to be measured/estimated in the primary network. Uncertain parameters may result in either decreasing the efficiency, or infeasibility of an RRA algorithm that is designed assuming perfect parameters. It is also required to address efficient and adaptive radio resource allocation among multiple secondary users. Other challenges include distributed implementations as well as developing analytical methods for performance evaluations of RRA algorithms. Performance analysis of RRA function sheds light on the fundamental performance bounds such as maximum achievable spectrum utilization, scaling property regarding the number of secondary users as well as other system trade-offs. Addressing these challenges is required for efficient adoption of SpS technology in full scale commercial wireless communication systems.

The applicant's proposal aims at the theoretical investigation of the impact of parameter uncertainty on the efficiency of the radio resource allocation in multi user secondary service spectrum sharing systems. This proposal also includes development of novel RRA techniques based on the theoretical investigations that differs from many conventional studies, in that practical concerns including robustness to uncertain input parameters, minimizing the level of inter and intra system signalling overhead and impact of multiple secondary service users are also taken into consideration.

The overall aims of this research proposal are: i) to develop an analytical framework which incorporates physical and higher layer functionalities into the system model in a multi secondary user environment and is able to model the impact of uncertainty in the parameters on the network performance, ii) to develop practical RRA algorithms based on this analytical framework to manage the impact of parameter uncertainty, and iii) to obtain fundamental performance limits for the multiple secondary service with uncertain parameters. The applicant's ultimate goal is to make SpS technology available to general public.

The proposed research project will ultimately provide impact for industry, government agencies, the economy and members of the public.

Industry beneficiaries will fall into two groups:
1.Infrastructure Hardware suppliers who will deliver the Spectrum Sharing (SpS) equipment and technology. e.g., Nokia Siemens Network (NSN), Ericsson and Alcatel-Lucent.

2.Cellular/Trunked Radio Network Operators of SpS technology, in particular, wireless service providers such as Vodafone, O2, Three, etc. and wireless access providers such as British Telecom (BT Openzone).

The hardware suppliers will benefit economically by gaining new technology which will help drive sales as network operators move to upgrade their network infrastructure to keep pace with competitors and end-user demands.

The network operators will benefit through the effective increase in network capacity that deployment of Spectrum Sharing (SpS) technology will provide. For cellular network operators, the radio spectrum bandwidth, which is leased through an auction process, is one of their most valuable assets costing billions of pounds. Maximising the effective use of this costly resource has the potential to significantly increase the profitability of these companies. Operators of trunked radio networks such as those built on the TETRA and APCO-25 standards (which are frequently employed by military, government and emergency service providers throughout the world) will also benefit. The cost of radio spectrum is also an issue for these network operators (though less than for cellular operators), but the ability to increase network capacity and effectively manage it will be highly beneficial and provide an improved quality of service to end-user organisations.

Regulatory agencies such as Ofcom will also benefit. As well as acting as the communication industry's watchdog, Ofcom also sets technical standards and allocates spectrum to network operators. One of Ofcom's legal responsibilities is to ensure that radio spectrum is used in the most effective way possible. The availability of SpS technology to the communication industry has the potential to help Ofcom in fulfilling this statutory duty. By encouraging network operators to deploy the SpS technology and ensuring that the regulatory framework does not impinge on the process of upgrading networks, Ofcom could not only be a beneficiary but also a partner in ensuring impact.

The public will also benefit from SpS technology in a number of ways. More efficient allocation of spectrum by cellular networks will lead to enhanced services for both telephony and mobile broadband. Additionally, there will be the potential for reduction in costs of services as cellular network operators make operating savings through more efficient use of their spectrum resources. The public will also benefit indirectly from the advantages gained by public service providers such as police forces through their greater efficiency in operations and lower operating costs.

Central government benefits include higher tax revenues due to the greater profitability of network operators in the UK. Also, provision of SpS technology in 4G cellular networks has the potential to greatly enhance rural broadband provision. Effective wireless broadband provision is the only means by which many communities are likely to receive fast internet services in the foreseeable future. The UK government is keen to promote fast rural broadband provision as a means of providing economic benefit and has already made a commitment to ensure all that all households can receive a minimum of 2Mbs internet connection by 2015. Future speed increases will be essential to ensure that rural areas are not economically disadvantaged through slow internet connections. Addition of SpS to 4G technology will maximise the available bandwidth for mobile broadband and help ensure that rural broadband provision keeps pace with the inevitable increase in demand