## Abstract

This paper presents a novel methodology for capturing the coupling between the different cells in both the uplink and downlink directions in a Wideband Code Division Multiple Access (WCDMA) scenario. It is based on the definition and computation of the gradient of the uplink cell load factor and the downlink transmitted power, which are the two main parameters that reflect the actual cell load in the two link directions. The paper shows that the gradient is able to capture the relevant information about the spatial distribution of traffic, which has an impact on cell performance. The proposed methodology is also used as the basis for defining and evaluating new Radio Resource Management (RRM) strategies that operate at a multi-cell level.

This is a preview of subscription content, log in to check access.

## References

- 1.
Bannister, J., Mather, P., & Coope, S. (2004).

*Convergence technologies for 3G networks*. John Wiley and Sons. - 2.
Tanner, R., & Woodard, J. (2004).

*WCDMA requirements and practical design*. John Wiley & Sons. - 3.
3GPP TR 25.922 v5.3.0, Radio resource management strategies.

- 4.
Sallent, O., Pérez-Romero, J., Agustí, R., & Casadevall, F. (2003). Provisioning multimedia wireless networks for better QoS: RRM strategies for 3G W-CDMA.

*IEEE Communications Magazine, 41*(2), 100–106. - 5.
Pérez-Romero, J., Sallent, O., & Agustí, R. (2004). A novel approach for multi-cell load control in WCDMA.

*IEE 3G Conference*, London. - 6.
Gilhousen, K. S., Jacobs, I. M., Padovani, R., Viterbi, A. J., Weaber, L. A., & Wheatley, C. E. III. (1991). On the capacity of a cellular CDMA system.

*IEEE Transactions on Vehicular Technology, 40*(2), 303–312. - 7.
Viterbi, A. J., Viterbi, A. M., & Zehavi, E. (1994). Other-cell interference in cellular power-controlled CDMA.

*IEEE Transactions on Communications, 42*(2/3/4), 1501–1504. - 8.
Holma, H., & Toskala, A. (2002).

*WCDMA for UMTS*(2nd ed.). John Wiley & Sons. - 9.
Lundin, E. G., Gunnarsson, F., & Gustafsson, F. (2003). Uplink load estimation in WCDMA.

*IEEE Wireless Communications and Networking*. WCNC 2003, 1669–1674. - 10.
Lui, Z., & El Zarki, M. (1994). SIR-based call admission control for DS-CDMA cellular systems.

*IEEE Journal on Selected Areas in Communications, 12*(4), 638–644. - 11.
Badia, L., Zorzi, M., & Gazzini, A. (2002). On the impact of user mobility on call admission control in WCDMA systems.

*56th IEEE VTC Fall Conference*, Vancouver, pp. 121–126. - 12.
Redana, S., & Capone, A. (2002). Received power-based call admission control techniques for UMTS uplink.

*56th IEEE VTC Fall Conference*, Vancouver, pp. 2206–2210. - 13.
Sallent, O., Pérez-Romero, J., & Agusti, R. (2003). Optimizing statistical uplink admission control for W-CDMA.

*57th IEEE VTC fall conference*, Orlando, USA. - 14.
Holma, H., & Laakso, J. (1999). Uplink admission control and soft capacity with MUD in CDMA.

*IEEE Vehicular Technology Conference in Fall 1999*, Amsterdam, pp. 431–435. - 15.
Gunnarsson, F., Geijer Lundin, E., Bark, G., & Wiberg, N. (2002). Uplink admission control in WCDMA based on relative load estimates.

*IEEE International Conference on Communications, ICC-2002*, pp. 3091–3095. - 16.
Capone, A., & Redana, S. (2001). Call admission control techniques for UMTS.

*54th IEEE VTC Fall Conference*, Atlantic City, pp. 959–929. - 17.
Dimitriou, N., Sfikas, G., & Tafazolli, R. (2000). Call admission policies for UMTS.

*51st IEEE VTC Spring Conference*, Tokyo, pp. 1420–1424. - 18.
Ho, C. J., Copeland, J. A., Lea, C. T., & Stuber, G. L. (2001). On call admission control in DS/CDMA cellular networks.

*IEEE Transactions on Vehicular Technology, 50*(6), 1328–1343. - 19.
Phan-Van, V., & Glisic, S. (2001). Radio resource management in CDMA cellular segments of multimedia wireless IP networks.

*The 4th International Symposium on Wireless Personal Multimedia Communications (WPMC)*, Aalborg, Denmark. - 20.
Knutsson, J., Butovitsch, P., Persson, M., & Yates, R. D. (1998). Downlink admission control strategies for CDMA systems in a Manhattan environment.

*IEEE Vehicular Technology Conference VTC*, pp.1453–1457. - 21.
Kazmi, M., Godlewski, P., & Cordier, C. (2000). Admission control strategy and scheduling algorithms for downlink packet transmission in WCDMA.

*52nd IEEE Vehicular Technology Conference Fall*, Boston, pp. 674–680. - 22.
Aïssa, S., Kuri, J., & Mermelstein, P. (2004). Call admission on the uplink and downlink of a CDMA system based on total received and transmitted powers.

*IEEE Transactions on Wireless Communications, 3*(6), 2407–2416. - 23.
Outes, J., Nielsen, L., Pedersen, K., & Mogensen, P. (2001). Multi-cell admission control for UMTS.

*VTC Spring Conference*, Vol. 2, pp. 987–991. - 24.
Pérez-Romero, J., Sallent, O., Agustí, R., & Sánchez, J. (2002). Managing radio network congestion in UTRA FDD.

*IEE Electronics Letters, 38*, 1384–1386. - 25.
Liu, T. K., & Silvester, J. A. (1998). Joint admission/congestion control for wireless CDMA systems supporting integrated services.

*IEEE Journal on Selected Areas in Communications, 16*(6), 845–857. - 26.
Passas, N., & Merakos, L. (1996). A graceful degradation method for congestion control in wireless personal communication networks.

*Proceedings of the IEEE Vehicular Technology Conference VTC*, pp. 126–130. - 27.
De Bernardi, R., Imbeni, D., Vignali, L., & Karlsson, M. (2000). Load control strategies for mixed services in WCDMA.

*51st IEEE Vehicular Technology Conference (VTC) Spring*, Tokio, pp. 825–829. - 28.
Rave, W., Kohler, T., Voigt, J., & Fettweis, G. (2001). Evaluation of load control strategies in an UTRA/FDD network.

*IEEE 53rd Vehicular Technology Conference Spring*, Rhodes, Greece, pp. 2710–2714. - 29.
3GPP TS 25.331 Radio Resource Control (RRC); Protocol Specification.

- 30.
3GPP TR 25.942 v5.3.0, Radio Frequency (RF) System Scenarios.

- 31.
3GPP TS 34.108 Common Test Environments for User Equipment (UE); conformance testing.

- 32.
Olmos, J. J., & Ruiz, S. (2002). Transport block error rates for UTRA-FDD downlink with transmission diversity and turbo coding.

*13th IEEE International Symposium on Personal, Indoor and Mobile Radio Communications PIMRC-2002*, Vol. 1, pp. 31–35. - 33.
Rautiainen, T. (2002). Breaking the hierarchical cell structure in WCDMA networks. In

*Proceedings of the 55th IEEE VTC Spring*, Vol. 1, pp.110–114.

## Acknowledgements

This work was carried out in the framework of project IST-AROMA (http://www.aroma-ist.upc.edu), which was partly funded by the European Community and by the Spanish Research Council (CICYT) under grant TEC2006-26873-E and COSMOS grant TEC2004-00518.

## Author information

## Appendix: Method of approximation for gradient computation

### Appendix: Method of approximation for gradient computation

The method described in Sect. 4 for the gradient computation of the uplink cell load factor and the downlink base station transmitted power gradient involves the solution of (*K* + 1) linear equation systems. Although the computational complexity would be feasible in real time, from a radio network engineering point of view a simpler formulation that maintains a sufficient degree of accuracy may be preferred. In this framework, this Appendix provides a method of approximation for gradient computation that can be used as an alternative to the method described in Sect. 4. Specifically, the method of approximation for Expression (22) is given by:

where it has been assumed that the term in the summation in (22) that most contributes to \(\partial\eta_{0}/\partial\eta_{k}\) is \(\partial\eta_{k}/\partial\eta_{k} = 1\).

For the downlink direction, a similar argument can be made, therefore, the approximation of (32) is given by:

In order to assess the accuracy of this approximation, various simulations were carried out in different scenarios using different traffic distributions. Various examples are shown in Figs. 1(b) and 2(b), which correspond to the uplink and downlink directions under the conditions discussed in Sect. 6.1. Notice that in both links the approximation underestimates the exact derivative due to the terms that were neglected when expressions (50) and (51) were obtained. In general, for other load conditions and spatial distributions the approximation holds quite well and errors below 10% were observed. Furthermore, as is shown in Sect. 7.1, the use of the exact or the approximate gradient has a very low impact on the performance that is observed with the gradient-based algorithms.

## Rights and permissions

## About this article

### Cite this article

Pérez-Romero, J., Sallent, O. & Agustí, R. A novel approach to smart multi-cell radio resource management based on load gradient calculations.
*Wireless Netw* **15, **709–726 (2009). https://doi.org/10.1007/s11276-007-0070-5

Published:

Issue Date:

### Keywords

- WCDMA
- Radio resource management
- Cellular systems
- Spatial traffic distribution