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- Impact of using CSS PHY and RTS/CTS Combined with Frame Concatenation in the IEEE 802.15.4 Non-beacon Enabled Mode PerformancePublication . Barroca, Norberto; Borges, Luís M.; Chatzimisios, Periklis; Velez, Fernando J.This paper studies the performance improvement of the IEEE 802.15.4 non-beacon-enabled mode originated by the inclusion of the Request-To-Send/Clear-To-Send (RTS/CTS) handshake mechanism resulting in frame concatenation. Under IEEE 802.15.4 employing RTS/CTS, the backoff procedure is not repeated for each data frame sent but only for each RTS/CTS set. The maximum throughput and minimum delay performance are mathematically derived for both the Chirp Spread Spectrum and Direct Sequence Spread Spectrum Physical layers for the 2.4 GHz band. Results show that the utilization of RTS/CTS significantly enhances the performance of IEEE 802.15.4 applied to healthcare in terms of bandwidth efficiency.
- Block acknowledgment mechanisms for the optimization of channel use in wireless sensor networksPublication . Barroca, Norberto; Velez, Fernando J.; Chatzimisios, PeriklisOne 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.
- Performance enhancement of IEEE 802.15.4 by employing RTS/CTS and frame concatenationPublication . Barroca, Norberto; Velez, Fernando J.; Borges, Luís M.; Chatzimisios, PeriklisIEEE 802.15.4 has been widely accepted as the de facto standard for wireless sensor networks (WSNs). However, as in their current solutions for medium access control (MAC) sub-layer protocols, channel efficiency has a margin for improvement, in this study, the authors evaluate the IEEE 802.15.4 MAC sub-layer performance by proposing to use the request-/clear-to-send (RTS/CTS) combined with frame concatenation and block acknowledgement (BACK) mechanism to optimise the channel use. The proposed solutions are studied in a distributed scenario with single-destination and single-rate frame aggregation. The throughput and delay performance is mathematically derived under channel environments without/with transmission errors for both the chirp spread spectrum and direct sequence spread spectrum physical layers for the 2.4 GHz Industrial, Scientific and Medical band. Simulation results successfully verify the authors’ proposed analytical model. For more than seven TX (aggregated frames) all the MAC sub-layer protocols employing RTS/CTS with frame concatenation (including sensor BACK MAC) allow for optimising channel use in WSNs, corresponding to 18–74% improvement in the maximum average throughput and minimum average delay, together with 3.3–14.1% decrease in energy consumption.
- Investigating Inclusiveness and Backward Compatibility of IEEE 802.11be Multi-link OperationPublication . Medda, Daniele; Chatzimisios, Periklis; Velez, Fernando J.; Iossifides, Athanasios; Wagen, Jean-FrédéricNowadays is not possible to avoid considering the coexistence and the fusion of different wireless technologies as completely separated entities. The ever-growing number of devices employing multi-RATs (Radio Access Technologies) that require continuous wireless connectivity is posing great challenges. Furthermore, the requirements in terms of both throughput and latency originated by the use cases, are pushing the current technologies to their limits, especially for indoor dense deployments that are usually covered by Wi-Fi. The IEEE 802.11 Working Group is currently tackling such challenges by working on a new amendment of the standard (namely 802.11be), which introduces, among other novelties, the multi-link operation (MLO). Through MLO, the target is to achieve simultaneous transmission over multiple bands to obtain massive bitrate up to 40 Gbps. The introduction of MLO poses challenges on the coexistence with older legacy devices in mixed networks. This contribution explores how the coexistence of legacy IEEE 802.11 devices and new IEEE 802.11be devices realizing the proposed multi-link feature can be improved by using an appropriate static band assignment policy. Another issue is how the overall network behaves when varying the number of devices and the legacy/new nodes ratio. Simulations for three different band allocation cases close to reality are developed. Performance results in terms of aggregated, average throughput and fairness are derived for different conditions.
- Block acknowledgment in IEEE 802.15.4 by employing DSSS and CSS PHY layersPublication . Barroca, Norberto; Borges, Luís M.; Velez, Fernando J.; Chatzimisios, PeriklisThe 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.
- IEEE 802.15.4 MAC layer performance enhancement by employing RTS/CTS combined with packet concatenationPublication . Barroca, Norberto; Borges, Luís M.; Velez, Fernando J.; Chatzimisios, PeriklisIEEE 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.