Dynamic Spectrum Management in Multi-Radio Access Technology (RAT) Cellular Systems

Abstract

Fixed Spectrum Allocation (FSA) results in suboptimal spectrum utilization, unbalanced system loading and the inability to adapt to system traffic variations when employed in multi-Radio Access Technology (RAT) systems. This paper proposes the use of flexible spectrum management techniques in multi-RAT systems. A Dynamic Spectrum Management (DSM) framework that addresses the shortcomings of FSA, while ensuring the reliable operation of all co-deployed RATs, is presented. Simulations for a system co-deploying HSPA and LTE show that the proposed framework outperforms FSA schemes and is capable of adapting to system traffic variations.Index Terms-Cellular systems, multi-RAT systems, spectrum management.

Unified Radio Access Network operation for Multi-Radio Access Technology cellular systems

“…9 and 10. As has been noted in [4], assigning spectrum at the system-level limits the ability of the ASR to adapt to system traffic variations; with the average performance of HSPA and LTE under ASR matching the DSM performance only when the average system loading maps to a feasible spectrum partitioning. Having the ability to optimally assign spectrum at each AP enables DSM to outperform ASR by up to 50% for both HSPA and LTE.…”

“…The DSM framework proposed in [4] enables independent spectrum assignment at each AP such that W ij t f 3 P 1j t P 2j t P Nj t f 3 provides optimal spectrum assignment based on AP traffic. Under Joint Resource Allocation (JRA), a unified resource allocation function directly allocates resources to all users at each AP based on user traffic demand and channel state…”

“…Following the 3GPP Multi-RAT system simulations model [13] and building on the model used in [4], a system with 19 wrap-around sectored base stations (57 cells) having an inter- site distance of 750 m is employed. LTE [12] and HSPA [14] are co-deployed over a contiguous 25 MHz band at 2 GHz.…”

“…While Fixed System-level Spectrum Assignment (FSSA) ensures consistent resource allocation, traffic variations within multi-RAT systems result in suboptimal spectrum utilization under FSSA [4]. On the other hand, gains from Dynamic Spectrum Management (DSM) techniques, proposed to improve spectrum utilization in multi-RAT systems [4], are restrained by disjoint resource allocation imposed by independent RAN operation as shown in Fig.…”

Markov approximation for Multi-RAT selection

“…The first step of the solution figured out user-to-RAT assignment and the second step of the solution allocated resources to WLAN and LTE users. Alsohaily and Sousa proposed a Dynamic Spectrum Management (DSM) framework in [4], while ensuring the reliable operation of all co-deployed RATs.…”