Dynamic load and spectrum usage management techniques can significantly improve the energy efficiency of mobile communications systems. This paper considers: (i) the opportunistic reallocation of traffic loads between bands to allow radio network equipment in the bands that the traffic is originated from to be powered down, and (ii) the opportunistic selection of more appropriate spectrum based on propagation characteristics to minimize necessary transmission power through improving propagation and/or reducing power leaking into co-channel cells in frequency reuse cases. This paper addresses the simulation of video, FTP and HTTP (web browsing) traffic sources for configurations representing LTE and HSDPA telecommunications networks, and shows that the opportunistic reallocation of users between bands to power down radio equipment achieves a significant saving of 50% or more in from-the-socket power. Furthermore, it shows that the opportunistic reallocation of users/links to minimize transmission power through using more appropriate propagation spectrum leads to a further modest reduction in from-the-socket power consumption.

IEEE 802.15.4 Medium Access Control (MAC) layer does not include the Request-To-Send/Clear-To-Send (RTS/CTS) handshake mechanism, in order to overcome the hidden node problem that affects Wireless Sensor Networks (WSNs). In this paper we propose and analyse the use of RTS/CTS in IEEE 802.15.4 for the nonbeacon-enable mode. The proposed solution shows that by considering the RTS/CTS mechanism combined with packet concatenation we improve the network performance in terms of maximum throughput, minimum delay and bandwidth effciency. In IEEE 802.15.4 with RTS/CTS, the backoff procedure process is not repeated for each data packet sent unlike the basic access mode of IEEE 802.15.4, but only for each RTS/CTS set. Therefore, the channel utilization is maximized by decreasing the deferral time period before transmitting a data packet. Our work introduces an analytical model capable of accounting the retransmission delay and the maximum number of backoff stages. The successful validation of our analytical model is carried out by comparison against simulation results by using the OMNeT++ simulator.

The IEEE 802.15.4 standard has been widely accepted as the de facto standard for Wireless Sensor Networks (WSNs), since it provides ultra-low complexity, cost and energy consumption for low-data rate wireless connectivity. However, one of the fundamental reasons for the IEEE 802.15.4 Medium Access Control (MAC) inefficiency is overhead. In the context of our research, we demonstrate that WSNs may benefit from packet concatenation. In this paper we introduce and study the employment of a block acknowledgment mechanisms in order to achieve enhanced channel efficiency in IEEE 802.15.4 nonbeacon-enabled networks for both the Chirp Spread Spectrum (CSS) and Direct Sequence Spread Spectrum (DSSS) Physical (PHY) layers for the 2.4 Industrial, Scientific and Medical (ISM) frequency band. The proposal of the two new innovative MAC sublayer mechanisms can also be considered as a future possible contribution to the standard itself. The throughput and delay performance is mathematically derived under ideal conditions, (i.e., a channel environment without transmission errors). The performance of the proposed schemes is compared against the IEEE 802.15.4 standard through extensive simulations by employing the OMNeT++ simulator. We demonstrate that, for both PHY layers, the network performance is significantly improved in terms of throughput, end-to-end delay and bandwidth efficiency.

This paper determines the cost/revenue performance of a mobile communication system in an IMT-Advanced scenario with integrated Common Radio Resource Management (iCRRM). The iCRRM performs classic CRRM functionalities jointly with Spectrum Aggregation (SA), being able to switch users between non-contiguous frequency bands. The SA scheduling is obtained with an optimized General Multi-Band Scheduling (GMBS) algorithm with the aim of cell throughput maximization. In particular, we investigate the dependence of the throughput on the cell coverage distance for the allocation of users over the 2 and 5 GHz bands for a single operator scenario under a constant average Signal to Interference-plus-Noise Ratio (SINR), for the same type of Radio Access Technology and both frequency bands. The operator has the availability of a non-shared 2 GHz band and has access to part (or all) of a shared frequency band at 5 GHz. An almost constant gain near 30 % was obtained with the proposed optimal solution compared to a system where users are first allocated in one of the two bands and later not able to handover between the bands. It is shown that the profit in percentage terms decreases as the cell radius increases. These results allow for evaluating the impact of the revenue from the channel in the total revenue and in the profit, defined as the difference between revenues and costs, in percentage. Maximum profits of about 1270, 585 and 240 % have been obtained for prices of 0.10, 0.05 and 0.025 €/MByte, respectively, when iCRRM is employed, while profits of 990, 440, and 170 % have been reached with no iCRRM, i.e., simple CRRM. Finally, an energy efficiency strategy is proposed and analyzed, showing that there is significant transmission power saving potential through the opportunistic reallocation scheme.

This work proposes a new scheme to coordinate the medium access of single-radio unlicensed users in a decentralized cognitive radio network. The proposed solution is based on two different stages. Unlicensed users randomly define the medium access sequence during the first stage and part of the second one. Then the nodes simply transmit their packets according to the reserved sequence. The performance of the proposed scheme is theoretically characterized in terms of the throughput achieved by unlicensed users and validated through simulation. Since a random access mechanism is used in the both stages, we also compare the performance of our proposal with a pure Slotted Aloha access scheme and an improved version of it. By comparing their performance, we conclude that the proposed scheme exhibits significant gains in terms of the throughput achieved by unlicensed users, and it can be recommended as a viable solution for future decentralized single radio cognitive networks.

This paper proposes an Integrated Common Radio Resource Management (iCRRM). The iCRRM performs classicCRRM functionalities jointly with SpectrumAggregation (SA), being able to switch users between non-contiguous frequency bands. The SA scheduling is obtained with an optimised General Multi-Band Scheduling algorithm with the aim of cell throughput maximisation. In particular, we investigate the dependence of the throughput on the cell coverage distance for the allocation of users over the 2 and 5 GHz bands for a single operator scenario under a constant average Signal to Interference-plus-Noise Ratio. For the performed evaluation, the same type of Radio Access Technology is considered for both frequency bands. The operator has the availability of a non-shared 2 GHz band and has access to part (or all) of a shared frequency band at 5 GHz. The performance gain, analysed in terms of data throughput, depends on the channel quality for each user in the considered bands which, in turn, is a function of the path loss, interference, noise, and the distance from the Base Station. An almost constant gain near 30% was obtained with the proposed optimal solution compared to a system where users are first allocated in one of the two bands and later not able to handover between the bands.

In Fixed WiMAX, the cost/revenue optimisation function for radio and network planning incorporates the cost of building and maintaining the infrastructure and the impact of the available resources on revenues. Supported throughput typically decreases with larger cells due to the implied greater average distance of users from the base station, although the use of subchannelisation can keep throughput steady with a larger cell radius. The use of sectored base stations facilitates selection of higher order modulation and coding schemes in the cell and can improve throughput; however, sectored equipment is more expensive. Fortuitously, using Relay Stations (RSs) can reduce the deployment cost of such systems. In such a context, if RSs are put into sleep mode during the night and at weekends when they are not necessary, important energy savings can be achieved. With relays, only the consideration of tri-sectored Base Station (BS) antennas with K = 3 (at the cost of extra channels, where nine channels corresponds to a bandwidth of 31.5 MHz) obtains values of system throughput comparable to those without using relays. This is due to the more favourable frame format that is employed under the use of tri-sectored BS antennas. This paper shows that the application of cell zooming in conjunction with relays going into sleep mode at times of low load achieves a notable power saving, corresponding to 10% saving in operation and maintenance cost on average. Moreover, as it is assumed that the DL sub-frame format cannot be changed to a more favourable one, economic performance is better when RSs are deployed. It is however important to highlight that in the absence of RSs, economic performance is still reasonable (for tri-sectored and omnidirectional BSs, 700–800% and 400–450% profit, respectively), compared with the case where RSs are deployed (∼1000 and ∼900% profit, respectively).

One of the fundamental reasons for the IEEE 802.15.4 standard Medium Access Control (MAC) inefficiency is overhead. The current paper proposes and analyses the Sensor Block Acknowledgment MAC (SBACK-MAC) protocol, a new innovative protocol that allows the aggregation of several acknowledgment responses in one special BACK Response packet. Two different solutions are addressed. The first one considers the SBACK-MAC protocol in the presence of BACK Request (concatenation) while the second one considers the SBACK-MAC in the absence of BACK Request (piggyback). The proposed solutions address a distributed scenario with single-destination and single-rate frame aggregation. The throughput and delay performance is mathematically derived under ideal conditions (a channel environment with no transmission errors). The proposed schemes are compared against the basic access mode of IEEE 802.15.4 through extensive simulations by employing the OM-NET++ simulator. We demonstrate that the network performance is significantly improved in terms of throughput and end-to-end delay.

The field of Wireless Body Area Networks (WBANs) has been growing considerably in the last years. A WBAN enables to monitor vital body signs through the placement of sensors on the human body and offers to patients more flexibility and mobility. In this paper, we examine the Quality of Service (QoS) performance metrics evaluation (single and multi-hop topology) of the Scheduled Channel Polling-MAC (SCP) protocol, whilst considering the IEEE 802.15.4 standard in the context of remote patient monitoring applications. We applied the MiXiM Framework (based on OMNeT++) in the network simulations. Our simulations results help to clarify some missing aspects in the original SCP protocol description. The IEEE 802.15.4 compliant Medium Access Control (MAC) is compared with the MAC layer in the absence of the IEEE 802.15.4, leading to similar values for the throughput in saturated conditions. The results also show that considering low duty cycles, the use of IEEE 802.15.4 leads to lower energy. For multi-hop experiments in high duty cycles, the energy consumptions are lower with the AT86RF231 transceiver, comparing with the CC1100 and CC2420. Future work includes the adaptation of the SCP protocol to the IEEE 802.15.6 standard, which has been specially developed to optimize the WBAN performance at the physical and MAC layers.

With nowadays evolution of wireless network technologies and the growth of novel wireless multimedia services it is critical for network and service providers to be able to assess user's perceptual multimedia quality, for commercial and technical reasons. As so, we present wireless network services and applications characterization requirements, updated to current specifications. We considered recommendations for some major regulations entities, such as the ITU, 3GPP, WiMAX Forum and the European project EU-MESH. In the case of audio and video applications, the latest and most used encoding schemes were addressed by considering the WiMAX Forum recommendations. In turn, as not only the Quality of Service (QoS) needs to be addressed, we propose a model for the mapping between QoS parameters and user's Quality of Experience (QoE) for multimedia applications. Measurable QoS parameters can be gathered throughout the network and mapped into an effective QoE estimation. The model has been obtained by means of mathematical regression and the fittings are validated by analysing the coefficient of determination, R2, between the results from our model and MOS experimental values. The achieved results are R2 = 0.94, 0.84 and 0.98 for gaming, video and audio, respectively. The corresponding mean square error is approximately zero in all cases.