Direct device-to-device (D2D) communications is regarded as a promising technology to provide low-power, highdata rate and low-latency services between end-users in the future 5G networks. However, it may not always be feasible to provide low-latency reliable communication between end-users due to the nature of mobility. For instance, the latency could be increased when several controlling nodes have to exchange D2D related information among each other. Moreover, the introduced signaling overhead due to D2D operation need to be minimized. Therefore, in this paper, we propose several mobility management solutions with their technical challenges and expected gains under the assumptions of 5G small cell networks.
Evolved UTRA (EUTRA) is currently under standardization within 3GPP as a long-term evolution (LTE) of Universal Terrestrial Radio Access (UTRA) air interface. Due to the potentially large number of VoIP users served in this system, related control signaling overhead for VoIP transmissions with traditional full dynamic scheduling scheme could become a bottleneck and limit the system capacity to a greater extent. In this paper, we present a semi-persistent packet scheduling scheme for VoIP to explore the capacity within the limitation of control channel resources. System level simulation results show that semi-persistent scheduling scheme can reduce control channel usage without using packet bundling technique. With 6 control channels, around 310 users per sector can be supported in 5 MHz bandwidth with both Discontinuous Reception (DRX) enabled and without packet bundling.
Long term evolution-wireless local area network (LTE-WLAN) aggregation (LWA) has recently emerged as a promising third generation partnership project (3GPP) Release 13 technology to efficiently aggregate LTE and WLAN at the packet data convergence protocol layer, allowing uplink traffic to be carried on LTE and downlink on both LTE and WLAN. This removes all the contention asymmetry problems of WLAN and allows an optimum usage of both licensed and unlicensed band for downlink. In this paper, we present a new feature of LWA, its flow control scheme, which controls how to aggregate downlink traffic in licensed and unlicensed bands. This aggregation technique exploits user equipment-based flow control feedback in the form of LWA status reports, and can be expanded to work with any number of frequency bands and radio technologies. The same concepts apply to 5G networks, although the performance evaluation provided here is in the context of LTE-Advanced Pro. Simulation results in a typical enterprise scenario show that LWA can enhance user performance up to 8 times over LTE-only, and 3.7 times over WLAN only networks, respectively. The impact of the file size and LWA status report frequency on network performance is also investigated.
INDEX TERMSCellular networks, long term evolution (LTE), wireless local area network (WLAN), LTE WLAN aggregation (LWA), flow control, aggregation.
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