Muhammad Kazmi

Handover within 3GPP LTE: Design Principles and Performance

The 3GPP LTE system has been designed to offer significantly higher data rates, higher system throughput, and lower latency for delay critical services. This improved performance has to be provided and guaranteed under various mobility conditions. Hence, handover (HO) and its performance are of high importance. This paper investigates the performance of the handover procedure within 3GPP LTE in terms of HO failure rate and the delay of the whole procedure. System level simulations within a typical urban propagation environment, with different User Equipment (UE) speeds, cell radii and traffic loads per cell have been performed. The entire layer 3 signalling exchanged via air interface is considered in the simulations. In addition, errors at the Layer 1 (L1) control channels are taken into account. Simulation results show that the handover procedure within 3GPP satisfies the goal of high performance mobility. Namely for cell radii up to 1 km and for UE speeds up to 120 km/h, the HO failure rate lies within the range of 0-2.2% even in high loaded systems. For medium and low loads even at speeds of 250 km/h, HO failure is below 1.3 %. In addition, simulation results show that the handover procedure is robust against L1 control channel errors.

Scheduling algorithms for HS-DSCH in a WCDMA mixed traffic scenario

Several scheduling algorithms are evaluated for the HS-DSCH channel in a WCDMA mixed traffic scenario. The traffic consists of FTP and Web surfing users. The maximum channel quality indicator (CQI) scheme serves users with the highest channel quality. The proportional fairness (PF) scheme tends to be fairer by prioritising users with higher channel quality (lower throughput). The weighted-queue-PF prioritises users with higher channel quality, lower throughput and those with longer queued-time. The results depict that the maximum system throughput is achieved by max CQI scheduling, which is pinch channel dependent. The max CQI scheme is also relatively fair to the FTP users. In case of Web surfing users, the proportionally fair scheduling is as good as the other schemes for the 10% worst users.

Evaluation of Inter-Frequency Quality Handover Criteria in E-UTRAN

In E-UTRAN multiple co-located carriers will typically be deployed requiring efficient inter-frequency (IF) handover procedures and algorithms for retaining service quality, better coverage and load balancing between the carriers. Five IF handover criteria using RSRP, RSRQ or combination thereof are investigated in synchronous and asynchronous E-UTRAN deployment scenarios. The results depict that an IF handover solely based on RSRP significantly increases number of handovers. Conversely the handover criterion based only on RSRQ reduces handovers but it slightly increases the packet loss rate. The overall best performance is achieved with the combined handover criterion, which uses both RSRP and RSRQ and thus guarantees that the received pilot strength as well as the signal quality stays within the desired limit after the handover.