Browsing by Author "Mumtaz, Shahid"
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- Performance evaluation of radio resource schedulers in LTE and 5G NR two-tier HetNetsPublication . Busari, Sherif Adeshina; Correia, Noélia; Mumtaz, Shahid; Rodriguez, Jonathan; Saghezchi, Firooz B.Network performance is critically dependent on the employed radio resource scheduler (RRS). The impact becomes even more significant in 5G ultra-dense networks due to the challenges of complicated base station distribution, user association, load balancing and inter-cell interference, among others. Using a combination of three popular schedulers (i.e., round robin (RR), proportional fairness (PF) and best channel quality indicator (BCQI)), we evaluate, in this work, the performance of two-tier heterogeneous networks where the different tiers employ the same or different RRSs. Using user throughput, cell capacity and system fairness as metrics, the results show that, on one hand, the average user throughput-system fairness tradeoff favours the use of the RR-PF combination (where the macrocell tier employs RR while the small cell tier uses PF). On the other hand, the BCQI-BCQI combination produces the highest network capacity, principally from about 5-10% of the total users, thereby sacrificing fair allocation of resources among the users. The results show that there is no globally optimal RRS combination across the metrics. As the mobile network operators have the freedom to deploy schedulers as they deem fit, the RRS combination can be selected to satisfy the performance targets of the respective use cases and deployment scenarios.
- Spectrum sharing for LTE and 5G-NR coexistencePublication . Busari, Sherif Adeshina; Correia, Noélia; Saghezchi, Firooz B.; Mumtaz, Shahid; Rodriguez, JonathanSpectrum sharing provides a rapid migration pathway toward 5G by enabling the coexistence of 4G LTE and 5G new radio (NR) that share the same spectrum. Due to significant differences in the LTE and 5G-NR air interfaces, several enablers are required to facilitate the spectrum sharing. In this study, we explore the coexistence features and investigate their impacts on network performance. For static and dynamic spectrum sharing scenarios, we assess the impacts of different spectrum sharing ratios, user ratios, MIMO configurations, mixed numerology profiles and traffic patterns on the user throughput and network capacities of spectrum sharing networks, compared with the LTE only and 5G-NR only networks with exclusive spectrum access. The key results show that spectrum sharing leads to a marginal capacity gain over LTE only network and achieves considerably lower capacity than the 5G-NR only network. Also, the results show that mixed numerology profiles between the LTE and 5G-NR lead to capacity losses due to inter-numerology interference. In addition, user and spectrum sharing ratios between LTE and 5G-NR have critical impacts on performance. Reduced spectrum per device as the number of 5G devices increases, higher signaling overhead and higher scheduling complexity are other limiting factors for spectrum sharing networks. The results show limited capacity benefits and reinforce spectrum sharing between LTE and 5G-NR as mainly an evolutionary path to accommodate 5G users in the same LTE spectrum while migrating to the fully-fledged 5G networks. For significant capacity increase, other features such as carrier aggregation, overlay of small cells and higher order MIMO would need to be incorporated into the network.