5G systems aim to achieve extremely high data rates, low end-to-end latency and ultra-low power consumption. Recently, there has been considerable interest in the design of 5G physical layer waveforms. One important candidate is Generalised Frequency Division Multiplexing (GFDM). In order to evaluate its performance and features, system- level studies should be undertaken in a range of scenarios. These studies, however, require highly complex computations if they are performed using bit-level simulators. In this paper, the Mutual Information (MI) based link quality model (PHY abstraction), which has been regularly used to implement system-level studies for Orthogonal Frequency Division Multiplexing (OFDM), is applied to GFDM. The performance of the GFDM waveform using this model and the bit-level simulation performance is measured using different channel types. Moreover, a system-level study for a GFDM based LTE-A system in a realistic scenario, using both a bit-level simulator and this abstraction model, has been studied and compared. The results reveal the accuracy of this model using realistic channel data. Based on these results, the PHY abstraction technique can be applied to evaluate the performance of GFDM based systems in an effective manner with low complexity. The maximum difference in the Packet Error Rate (PER) and throughput results in the abstraction case compared to bit-level simulation does not exceed 4% whilst offering a simulation time saving reduction of around 62,000 times.

This paper presents a novel Time Domain (TD) based Multiple-Input Multiple Output (MIMO) implementation of the Expectation-Maximization (EM) algorithm. The algorithm is able to achieve Maximum Likelihood (ML) performance with reduced complexity. Results show how performance superior to the Recursive Least Square (RLS) algorithm, in terms of both convergence and residual Mean Squared Error (MSE), can be achieved with comparable complexity. The channel estimation technique is combined with a new TD based MIMO loop interference cancellation system for wireless relays. Performance results for a 2×2 Downlink (DL) Long Term Evolution (LTE) system are provided for both single-stream transmission with Maximal Ratio Combining (MRC) and dual-stream transmission with Spatial Multiplexing (SM). Results are shown at both low mobility and high mobility, with our EM algorithm showing up to a 2dB improvement in the Error Vector Magnitude (EVM) in the MRC case at 60kmph compared to the RLS.

In this paper the throughput and packet error rate for an in-home 802.11n network is theoretically derived for two different types of 3x3 antenna configurations. Our first configuration assumes the use of three low directivity omni-dectional elements. The second arrangement makes use of three orthogonally orientated directional elements. The spatial and temporal characteristics of the in-home channels are modelled using 3D ray tracing and combined with appropriately orientated complex polarmetric patterns for each antenna element. Physical layer throughput is computed for all modulation and coding schemes using a received bit information rate abstraction technique. The theory shows that directional antennas outperform the omni-directional devices in most cases. Directional elements show increased sensitivity to orientation, however for 83% of locations and orientations they still result in throughput enhancement. Directional antennas provide a 33% improvement in average data rate for random client orientations, improving to 52% with optimum alignment to the multipath.

This paper explores rules and defines cross layer parameters that enhance the received video quality per unit bandwidth while observing strict video QoS for unicast video transmission over mobile WiMAX. Channel capacity and goodput are estimated using a detailed MAC/PHY simulator. The simulator supports link adaptation of the PHY layer Modulation and Coding Scheme (MCS) alongside MAC layer Automatic Repeat Request (ARQ). A new performance indicator, PSNR per Hz, is defined to capture the video PSNR attained for a given effective bandwidth. For the 3GPP urban micro channel, MCS and MAC layer block lifetime are jointly determined as a function of average channel SNR in order to enhance video PSNR and goodput. At low SNR higher level QAM is inefficient (as a result of excessive MAC layer ARQ or high packet error rate) for video transfer. Results show that video efficiency improves for block lifetimes up to 100ms, since the greater use of ARQ enables more spectrally efficient MCS modes to be applied.

This paper presents results from a novel OFDMA multi-cell mobile broadband system-level simulator. The tool is used to statistically characterize uplink and downlink inter-cell interference. Fully loaded interference studies cannot be performed on real-world networks until they have been fully deployed. As such, interference analysis and management must be accurately performed pre- deployment using detailed network simulators. This paper discusses our simulator architecture and the steps necessary to reduce computational complexity inherent in such simulations. The paper then demonstrates the impact of inter-cell interference in OFDMA networks. The results demonstrate that it is the frame-to-frame fluctuations in interference, and not the received signal level, that dominate inaccuracy in the Channel Quality Index (CQI). CQI errors lead to the wrong MCS mode being chosen by the AMC algorithm and this leads to throughput reduction. Results show that this problem is exacerbated by high vehicular speeds and the absence of interference randomization. Compared to ideal MCS selection, throughput reductions of up to 45% are reported.

Throughput and packet error rate are analysed in a home environment for two different 3×3 wireless LAN solutions. A 3×3 EBF approach (using three radio chains) is compared with a reduced cost 2×2 architecture (using two radio chains). In the 2×2 solution the optimum antenna pair is selected from the same set of three antennas at the AP and client. The impact of directional, as well as omni- directional, antenna elements is considered. The spatial and temporal characteristics of the in-home channels are modelled using 3D ray tracing and combined with appropriately orientated complex polarmetric patterns for each antenna element. Physical layer throughput is calculated for all modulation and coding schemes and (for the 2×2 case) all possible antenna combinations using a novel received bit mutual information rate abstraction technique. Results show that antenna number, pattern and orientation all play a key role in determining the performance of an 802.11n system. As expected, 3×3 EBF outperforms the 2×2 solution; however, with optimum antenna selection the performance of 2×2 EBF is competitive, especially when directional antennas are used at low signal to noise ratios. For distant rooms, 3×3 EBF is only 15% better (in terms of throughput) than 2×2 EBF when directional antennas and dynamic antenna selection are applied. 2×2 EBF with omni antennas results in a 45% reduction in throughput (compared with 3×3 EBF).

This paper presents results from a novel OFDMA multi-cell mobile broadband system level simulator. The tool is used to statistically characterize uplink and downlink inter-cell interference. Without suitable interference management, multi-billion dollar networks can collapse under the strain of heavy traffic loads. Fully loaded interference studies cannot be performed on the network until it has been fully deployed. As such, interference analysis and management must be accurately performed pre-deployment using detailed network simulators. System level simulation is a highly computationally intensive procedure. This paper discusses the simulator architecture (and steps taken to reduce computational complexity) and then demonstrates the impact of inter-cell interference in OFDMA networks. In an interference limited scenario the results demonstrate that it is the frame-to-frame fluctuations in interference, and not the received signal level, that dominate inaccuracies in the Channel Quality Index (CQI) prediction. CQI is used in the fast link-adaptation process to select the MCS mode for each user on a frame-by-frame basis. Results show that incorrect Modulation and Coding Scheme (MCS) modes are chosen up to 40% of the time when the CQI is delayed by 3 frames and the user is interference limited. Perfect MCS selection is then shown to improve user throughput by up to 50%.

The end-to-end performance of applications in broadband wireless networks is a key concern from the user perspective. Mobile WiMAX is designed to support a wide range of different applications including media streaming, voice-over- IP (VoIP), video conferencing, and web browsing. All of these applications require different levels of quality of service (QoS) and this imposes a variety of different performance requirements on the WiMAX physical (PHY) and medium access control (MAC) layers. For example, TCP-based applications such as FTP or Web-browsing use automatic-repeat-request (ARQ) to tolerate a relatively high PHY packet error rate (PER), whilst a UDP-based application such as video streaming requires very low PER due to the lack of ARQ. This means that the same WiMAX system configuration needs to be able to provide different performance levels for different types of applications in order to operate efficiently. This paper analyses and compares the performance of a multi-input multi-output (MIMO) mobile WiMAX system in terms of achievable throughput and operating range for different PHY PER requirements. The paper shows that TCP applications can achieve higher throughputs and operating ranges due to higher PER tolerance. It also shows that this important QoS parameter affects the AMC switching points. Cross-layer interaction is required between the PHY and the scheduler in the MAC layer in order to efficiently fulfil the various QoS requirements at the application layer.

Research in ATM management has delegated control functions from the ATM switch into higher level open control architectures. For example, functions such as call admission control are implemented within such a control architecture rather than as an integral part of the switch. The association between the switch fabric and the switch control functions is made less strict, allowing, for example, a single entity to perform routing for a group of switches. This greater flexibility in the provision of control is accompanied by an increase in complexity resulting from the possibility of making control decisions remotely from the controlled network element. The location of the controller in relation to the fabric is not just an implementation issue; it has a large impact on the way we handle traditional operation and maintenance (OAM) functions. For example, recovering from partial failure of the network is problematic when the controlling entity is communicating with the switch it controls across that same network. Most research into such control architectures has concentrated on the advantages of increasing flexibility; little work has looked at how the traditional techniques for creating robust networks can be adapted for use in this environment. Mobile software agents can move to where their functions are carried out. When an agent has moved across the network, it executes its function there. The function will not fail due to network problems. They can also reduce the amount of management state that needs to be carried across the network for control purposes. This is important when recovering from failure since the network is stressed and minimal expectations should be placed on its behavior. We show how mobile agents can be used within an open control architecture in order to implement robust operation and maintenance functions. We explain in some detail our work in implementing one such function.