: Blockchain Division Multiple Access for IEEE 802.11

Student thesis: Doctoral ThesisDoctor of Philosophy


Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) has become the de facto multiple access mechanism for Wireless Local Area Network (WLAN). WLAN introduces an element of flexibility into local area network (LAN) architecture, providing mobility to users, while still ensuring network access via a wireless medium. The wireless LAN, as seen in CSMA/CA, is built on contention for the transmission medium. With contention, there is bound to be collisions, so a necessary step was the inclusion of RTS and CTS frames for added avoidance. Furthermore, the through-put in the BSS reduces as the number of devices contending for the transmission medium increase. The goodput falls below the throughput because packets need to be retransmitted, as a result of collisions. Therefore, we introduce a novel multiple access protocol titled BCDMA. The main idea of this novel protocol is to introduce Blockchain technology as the transmission medium management tool. The Blockchain is a technology that allows multiple parties to securely interact and come to decisive conclusions without needing an intermediary. For example, accurate identity authentication, cryptographic proofs for transactions, secure, traceable payments, etc. These are attributes that we draw on for our novel BCDMA protocol. Similar to TDMA, BCDMA allocates access to the transmission medium using dedicated time slots. This allocation ensures a certain level of throughput due to devices transmitting strictly within their time slot. BCDMA also has a higher good-put, given that there are no retransmissions as a result of collisions. By treating the time-slots as assets on a smart contract, BCDMA allocates time-slots to devices. BCDMA further increases the user experience in the BSS by offering added services. The presence of cryptocurrency in Blockchain technology provides a means to offer added services to devices, for a price. For example, in BCDMA, devices with strin-gent latency constraints can purchase more slots. Furthermore, these transactions, as well as the identity of the signees, are cryptographically traceable. Base knowledge of block latency and transaction confirmation speed in the current state of the art Blockchain technology would critically limit any possible integration of Blockchain technology into WLAN. However, by adjusting the Blockchain network configurations, blocks can be mined faster, and decisions on transactions can be received quicker. Although, these extreme configurations reduce the security in the Blockchain network, hence increasing the probability of successful attacks. Nevertheless, BCDMA achieves higher goodput compared to CSMA/CA. The proposed BCDMA protocol yields improvements of > 85% throughput when the load capacity of the network is near saturation. Furthermore, we observe qualita-tive improvements in terms of security with regards to both station and AP authentication within the WLAN. By using permissioned ledgers, BCDMA is not prone to the attack rate experienced in public networks; however, we simulate a selfish miner attack in our network achieving a success rate of 8 blocks in the most extended fork, with the attacker owning 30% of the mining power. Moreover, implementing the whisper protocol for multi-BSS communication increases the security in disseminating authentication credentials.
Date of Award1 Jun 2021
Original languageEnglish
Awarding Institution
  • King's College London
SupervisorMischa Dohler (Supervisor) & Peter McBurney (Supervisor)

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