Martti Moisio

System performance of LTE and IEEE 802.11 coexisting on a shared frequency band

This paper presents the system performance analysis of 3GPP Long-Term Evolution (LTE) and IEEE 802.11 Wireless Local Area Networks (WLAN) in a situation where LTE downlink (DL) has been expanded over to unlicensed frequency band usually used by WLAN. Simple fractional bandwidth sharing mechanism is used to allow both technologies to transmit. The system performance is evaluated by means of fully dynamic network simulations.

Channel Quality Indication Reporting Schemes for UTRAN Long Term Evolution Downlink

In this paper we evaluate the performance of channel quality indicator (CQI) reporting schemes in 3GPP UTRAN long term evolution (LTE) downlink (DL). In LTE, time and frequency dependent CQI is needed for DL packet scheduling (PS) and fast link adaptation (LA). Studies have indicated that frequency domain PS (FD-PS) and LA are essential techniques in improving the LTE performance, giving e.g. both cell throughput and coverage gain of around 40 % over a distributed multiplexing scheme. However, there is a tradeoff with signaling overhead related to the CQI feedback and overall LA and PS performance, which is rather overlooked in the literature. We analyze four different CQI reporting schemes with respect to system spectral efficiency and conclude that the best-M average and threshold based CQI reporting schemes seem to be the most promising in terms of the compromise between system performance and signaling overhead.

Voice-Over-IP Performance in UTRA Long Term Evolution Downlink

In this paper, we study voice-over-IP (VoIP) performance in UTRA long term evolution (LTE) downlink (DL). We have utilized fully dynamic system simulations to study the VoIP adaptive multi-rate (AMR) 12.2 codec capacity in four different 3GPP simulation cases. The effects of link adaptation (LA), packet bundling, control channel capacity and number of HARQ processes on VoIP capacity have also been considered. The results present the absolute VoIP capacity numbers of LTE DL. We also show that LA together with packet bundling provides clear gain on the VoIP capacity, because more VoIP packets can be scheduled in each TTI. Also, the control channel limitations can be effectively compensated by packet bundling.

Smart mobility management for D2D communications in 5G networks

Direct device-to-device (D2D) communications is regarded as a promising technology to provide low-power, high-data 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.

Comparison of effective SINR mapping with traditional AVI approach for modeling packet error rate in multi–state channel

This paper provides an overview and comparison of traditional and advanced Link-to-System (L2S) interface mappings used in system level simulations to evaluate link performance in terms of packet error rate (PER). An Actual Value Interface (AVI) as traditional L2S interface is compared with an Effective SINR Mapping (ESM) as advanced L2S interface. This comparison is able to highlight the main differences in prediction of multi-state channel performance effecting on final data throughput, delay of data packets and required CPU time. Furthermore, this paper proposes an improved version of AVI method in order to improve the accuracy of system performance estimation. The comparison results show that in case of multi-state OFDM system, highest accuracy is achieved with Mutual Information ESM (MIESM) method and relatively good accuracy with the exponential ESM (EESM) method.

Impact of Control Channel Limitations on the LTE VoIP Capacity

In this paper, we present a fully dynamic simulative analysis of the Downlink (DL) Voice-over-IP (VoIP) performance in 3G Long Term Evolution (LTE) with both Uplink (UL) and DL control channel constraints. In UL the Physical Uplink Control Channel (PUCCH) capacity affects the Channel Quality Indicator (CQI) resolution and in DL the Physical Downlink Control Channel (PDCCH) capacity has an impact to the amount of multiplexed users per Transmission Time Interval (TTI). The results indicate that with realistic control channel assumptions, semi-persistent packet scheduling outperforms dynamic packet scheduling.

Performance of VoIP with Mobility in UTRA Long Term Evolution

In this paper, we study VoIP capacity in UTRA Long Term Evolution downlink under different mobility conditions. Since LTE is designed to be a wide area system supporting very high mobility, VoIP capacity for different mobility conditions is an important measure for the LTE system. We show how the mobility dynamics affect the VoIP capacity, using a dynamic system simulator to model the effects of both Robust Header Compression (ROHC) and handovers. The results indicate that the effect of non-ideal ROHC to VoIP system capacity is minimal, especially when compared to the mobility effects to system capacity.

Persistent packet scheduling performance for Voice-over-IP in evolved UTRAN downlink

In this paper we present and analyze different packet scheduling mechanisms for Voice-over-IP (VoIP) in UTRAN Long Term Evolution Downlink. Dynamic packet scheduling provides multi-user and frequency domain scheduling gain, but at the expence of high control channel utilization. VoIP service with high number of simultaneous users and small packets can cause the control channel consumption to be the bottleneck for VoIP performance. Thus several persistent packet scheduling mechanisms have been proposed in 3GPP, such as fully persistent, talk-spurt based persistent and semi-persistent packet scheduling. We analyze the VoIP performance of different packet scheduling mechanisms by using fully dynamic system level simulations. We observe that with dynamic packet scheduling the VoIP capacity is restricted by the control channel capacity, whereas with persistent scheduling the capacity is restricted by the delay budget due to worse PRB SINR and resulting increased number of retransmissions.

Mixed traffic packet scheduling in UTRAN Long Term Evolution Downlink

In this paper we study the packet scheduling of mixed traffic in UTRAN long term evolution downlink. A dynamic packet scheduling (PS) architecture with service classification, queue specific sorting and scheduling algorithms as well as frequency domain PS has been presented to differentiate scheduling of different traffic classes. Simulation results have been provided by using control data, voice-over-IP (VoIP) and best effort (BE) traffic types. The results show that VoIP prioritizing is needed to keep the VoIP UEs satisfied. However, the strict prioritizing decreases the system spectral efficiency to around 70-80% of the pure BE spectral efficiency due to small VoIP packets.

MIMO performance evaluation in UTRAN Long Term Evolution downlink

In this paper we evaluate the dual stream multiple-input multiple-output (MIMO) performance for two rank adaptation schemes in 3GPP UTRAN long term evolution downlink. A capacity-based rank adaptation scheme as a transmission mode selection algorithm is compared to a throughput-based rank adaptation scheme by means of system level simulations run in four typical 3GPP scenarios. Additionally, the effect of mobility to system performance with multi-stream transmission is investigated in a 3GPP scenario with higher cell radius. Simulation results have been provided by using fully dynamic system level simulator. Results show that in all low-mobility (3 kmph) cases the evaluated MIMO transmission schemes provide 10iquest20% gain in terms of average and cell edge spectral efficiency. Further, we show that mobility has a clear effect on MIMO spectral efficiency and that the MIMO multiplexing gain is clearly reduced with higher user velocity. Finally, it is shown that the studied low-complexity capacity-based rank adaptation is able to reach similar performance compared to throughput-based adaptation.