We study the uplink control signaling in 3GPP-Long Term Evolution (LTE) systems. Specifically, we propose a precoding method that uses complex-field coding (CFC) to improve the performance of the PUCCH format 2 control signaling. In the case of perfect channel state information (CSI) at the receiver and with a single receive antenna, the proposed method offers significant gains compared to the coding currently used in 3GPP-LTE. However the gains are marginal with two receive antennas. In order to examine the impact of channel estimation errors, we also derive the optimal detector for the case of imperfect receiver CSI, both for conventional coding and for the proposed CFC method.

Control signaling strategies for scheduling information in cellular OFDM systems are studied. A single-cell multiuser system model is formulated that provides system capacity estimates accounting for the signaling overhead. Different scheduling granularities are considered, including the one used in the specifications for the 3G Long Term Evolution (LTE). A greedy scheduling method is assumed, where each resource is assigned to the user for which it can support the highest number of bits. The simulation results indicate that the cost of control signaling does not outweigh the scheduling gain, when compared with a simple round-robin scheme that does not need signaling of scheduling information. Furthermore, in the studied scenario, joint coding and signaling of scheduling information over all selected users is found to be superior to separate coding and signaling for each user. The results also indicate that the scheduling granularity used for LTE provides better performance than the full granularity.

This paper discusses the requirements on future radio access and, based on the requirements, proposes a framework for such a system. The proposed system based on orthogonal frequency-division multiplexing supports very low latencies and data rates up to 100 Mb/s with wide area coverage and 1 Gb/s with local area coverage. Spectrum flexibility is identified as one main requirement for future systems, and the proposed framework can be deployed in a wide range of spectrum allocations with bandwidths ranging from 2.5 to 100 MHz. Multihop relaying, useful to extend the range for the high data rates, and multiple-antenna configurations are integral parts of the framework. A packet-centric approach is taken for the dataflow processing, implying that the scheduling mechanism and the retransmission protocol operate on complete packets rather than segments thereof, thus allowing for cross-layer optimization. Finally, numerical evaluations are provided, illustrating the feasibility of future very wideband radio access.

Activity-based uplink load estimation is considered for WCDMA. By taking the user activity explicitly into account, the method is suitable for a scenario where services with very different activity levels use the same RAB. Scenarios with different mixes of email and MMS (multimedia messaging service) traffic are considered. Simulations indicate that the method provides good accuracy in situations where methods without activity estimation may overestimate the uplink load with about 3 dB.

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.

This paper discusses the TPC detection performance in soft handover in WCDMA. A simple TPC commands combining method is evaluated and an improved TPC combining method is proposed. Results show that although the simple combining method fulfills the 3GPP requirements, it does not perform well from the system performance perspective. The proposed combining method significantly improves the system performance.

When operating a cellular radio system at nearly full capacity, admitting yet another user may jeopardize the stability of the system as well as the performance of the individual users. Therefore, proper admission control is crucial. Prior art includes algorithms which limit the number of users or the uplink interference per cell. Both are known to yield roughly the same performance, but the former is difficult to configure, and the latter is based on a quantity which is hard to measure accurately. The core idea in this work is to predict the relative load of the system directly, given that a user is admitted. Then, the user will be admitted if the predicted load in the specific cell, and in its neighbors, is below some threshold. The proposed uplink relative load estimate is focused on WCDMA. It utilizes measurements readily available in that system, either periodically scheduled or from handover events. Multi-services are naturally handled, and availability of high data-rate services are automatically limited with respect to coverage, compared to services of lower data-rate. Simulations indicate that the admission control operates satisfactorily in different traffic situations with a universal parameter setting. Furthermore, the reporting overhead with periodical measurements can be avoided, since handover event-driven measurements yield roughly the same performance.

Two resource assignment algorithms are studied and evaluated for best-effort services in the downlink of WCDMA. The basic idea is to update users' bitrate periodically in response to traffic and channel variations. Both schemes are based on power fairness, which means users are allowed to have the same power consumption. However, one scheme provides minimum guaranteed bitrate to all the users, whereas the second algorithm does not give any guarantee. The guaranteed and non-guaranteed schemes provide a throughput gain in the order of 15-20% and 55-60% with respect to the reference scenarios. The continuous execution of the schemes also unifies admission and congestion controls into one principal algorithm.

This paper deals with the performance analysis of a CDMA downlink in multipath fading channels. An approximate expression for the demodulated signal-to-noise ratio is developed for a conventional RAKE receiver. The expression includes an orthogonality factor that quantifies the performance gain of using orthogonal spreading codes in the presence of a time-dispersive channel. A comparison with simulation results shows that the accuracy of the expression is high in various combinations of desired signal, orthogonal and non-orthogonal intra-cell interference, and AWGN. The numerical results also show that not only the strength of individual rays but also their relative phases and delays determine the value of the orthogonality factor.