A performance analysis of channel fragmentation in dynamic spectrum access systems
Dynamic Spectrum Access systems offer temporarily available spectrum to opportunistic users capable of spreading transmissions over a number of non-contiguous subchannels. Such methods can be highly beneficial in terms of spectrum utilization, but excessive fragmentation degrades performance and hence off-sets the benefits. To get some insight into acceptable levels of fragmentation, we present experimental and analytical results derived from a mathematical model. According to the model, a system operates at capacity serving requests for bandwidth by assigning a collection of one or more gaps of unused bandwidth to each request as bandwidth becomes available. Our main result is a proof that, even if fragments can be arbitrarily small, the system remains stable in the sense that the average total number of fragments remains bounded. Within the class of dynamic fragmentation models, including models of dynamic storage allocation that have been around for many decades, this result appears to be the first of its kind.
In addition, we provide extensive experimental results that describe behavior, at times unexpected, of fragmentation as parameter values are varied. Different scanning rules for searching gaps of available spectrum, all covered by the above stability result, are also studied. Our model applies to dynamic linked-list storage allocation, and provides a novel analysis in that domain. We prove that, interestingly, a version of the 50 % rule of the classical, non-fragmented allocation model holds for the new model as well. Overall, the paper provides insights into the behavior of practical fragmentation algorithms.
- Akyildiz, I.F., Lee, W.Y., Vuran, M.C., Mohanty, S. (2006) NeXt generation/dynamic spectrum access/cognitive radio wireless networks: a survey. Comput. Netw. 50: pp. 2127-2159 CrossRef
- Asmussen, S. (1987) Applied Probability and Queues. Springer, New York
- Coffman, E., Robert, P., Simatos, F., Tarumi, S., Zussman, G. (2010) Channel fragmentation in dynamic spectrum access systems—a theoretical study. Proc. ACM SIGMETRICS’10.
- Coffman, E.G., Puhalskii, A.A., Reiman, M.I. (1991) Storage limited queues in heavy traffic. Probab. Eng. Inf. Sci. 5: pp. 499-522 CrossRef
- Coffman, E.G., Reiman, M.I. (1983) Diffusion approximations for storage processes in computer systems. Proc. ACM SIGMETRICS’83.
- Dvoretsky, A., Robbins, H. (1964) On the ‘parking’ problem. Publ. Math. Inst. Hung. Acad. Sci. 9: pp. 209-226
- FCC: 03-222. Notice of proposed rulemaking (2003)
- FCC: 08-260. Second report and order, ET Docket No. 04-186, unlicensed operation in the TV broadcast bands (2008)
- Feller, W. (1966) An Introduction to Probability Theory and Its Applications. Wiley, New York
- Ghasemi, A., Sousa, E. (2008) Spectrum sensing in cognitive radio networks: requirements, challenges and design trade-offs. IEEE Commun. 46: pp. 32-39 CrossRef
- Hajek, B. (1982) Hitting-time and occupation-time bounds implied by drift analysis with applications. Adv. Appl. Probab. 14: pp. 502-525 CrossRef
- Jia, J., Zhang, Q., Shen, X. (2008) HC-MAC: a hardware-constrained cognitive MAC for efficient spectrum management. IEEE J. Sel. Areas Commun. 26: pp. 106-117 CrossRef
- Kipnis, C., Robert, P. (1990) A dynamic storage process. Stoch. Process. Appl. 34: pp. 155-169 CrossRef
- Knuth, D.E. (1997) The Art of Computer Programming. Addison Wesley Longman Publishing Co., Redwood City
- Mahmoud, H., Yucek, T., Arslan, H. (2009) OFDM for cognitive radio: merits and challenges. IEEE Wirel. Commun. 16: pp. 6-15 CrossRef
- Meyn, S., Tweedie, R.L. (2009) Markov Chains and Stochastic Stability. Cambridge University Press, Cambridge
- Mitola, J. III: Cognitive radio: an integrated agent architecture for software defined radio. Ph.D. thesis, Doctor of Technology, Royal Inst. Technol. (KTH), Stockholm, Sweden (2000)
- Poston, J.D., Horne, W.D. (2005) Discontiguous OFDM considerations for dynamic spectrum access in idle TV channels. Proc. IEEE DySPAN’05.
- Rajbanshi, R., Wyglinski, A.M., Minden, G.J. OFDM-based cognitive radios for dynamic spectrum access networks. In: Bhargava, V.K., Hossain, E. eds. (2007) Cognitive Wireless Communication Networks. Springer, Berlin, pp. 165-188 CrossRef
- Shukla, A., Willamson, B., Burns, J., Burbidge, E., Taylor, A., Robinson, D.: A study for the provision of aggregation of frequency to provide wider bandwidth services. Tech. rep., QinetiQ (2006)
- Tarumi, S.: Analysis of channel fragmentation in dynamic spectrum access networks. Ph.D. thesis, Columbia Universtiy, Electrical Engineering (2010)
- Weiss, T.A., Jondral, F.K. (2004) Spectrum pooling: an innovative strategy for the enhancement of spectrum efficiency. IEEE Commun. 42: pp. S8-14 CrossRef
- Yuan, Y., Bahl, P., Chandra, R., Moscibroda, T., Wu, Y. (2007) Allocating dynamic time-spectrum blocks in cognitive radio networks. Proc. ACM MobiHoc’07.
- A performance analysis of channel fragmentation in dynamic spectrum access systems
- Open Access
- Available under Open Access This content is freely available online to anyone, anywhere at any time.
Volume 71, Issue 3 , pp 293-320
- Cover Date
- Print ISSN
- Online ISSN
- Springer US
- Additional Links
- Dynamic spectrum access
- Ergodicity of Markov chains
- Cognitive radio
- Lyapunov function
- Industry Sectors