Leonardo Lanante

Network densification has led to a renewed emphasis on means to improve aggregate network throughput for next-gen (High Efficiency) WLANs. The introduction of BSS color feature in support of enhanced spatial reuse sets IEEE 802.11ax apart from legacy WLAN. BSS color enables stations within a network to identify whether a transmission originates from an overlapped BSS and provides an option for mitigating the exposed node problem by allowing it to transmit (over the on-going OBSS transmission) albeit with reduced transmit power. As a result, distances between networks can be reduced, thereby improving the area spectral efficiency. To the best of our knowledge, this is the first work to develop an analytical model for IEEE 802.11ax spatial reuse that provides useful rules for optimizing network area throughput. We show that the spatial reuse gain is tightly linked to the interference range properties of each BSS in the network. Further, the analytical model predictions are validated and expanded via definitive ns-3 simulation results exploiting a recently concluded upgrade to 802.11 WLAN network stack (that implemented the necessary spatial reuse features).

Channel bonding in IEEE 802.11 wireless LANs is a technique whereby adjacent 20MHz channels are ‘bonded’ to create a wider bandwidth channel that supports higher data rate transmissions. Although rate improvements due to channel bonding has been shown in sparse wireless LAN environments, its effectiveness in dense scenarios requires further exploration due to increased sensitivity to interference from overlapping co-channel basic service sets. With the newly finalized 802.11ax standard supporting enhanced spatial reuse feature, its impact on the expected gains from channel bonding needs careful analysis. In this work, we propose a new analytical framework that accurately models the performance of channel bonding as a function of both PHY and MAC parameters for a dense network scenario. A new channel bonding algorithm that is robust to overlapped co-channel interference is described, i.e. it preserves channel bonding gains by intelligently choosing the channel bonding bandwidth based on network conditions and parameters that are readily available to all stations, critically the modulation scheme chosen for packet transmission. The predicted gains of the proposed algorithm are verified via comprehensive simulations conducted with the open source network simulator ns-3.

IEEE 802.11ax partitions a regular 20MHz channel into smaller sub-channels called resource units to support simultaneous multiuser operation using orthogonal frequency division multiple access (OFDMA). Uplink OFDMA random access (UORA) in IEEE 802.11ax allows stations to transmit via a scheduled random access mechanism. UORA is initiated via a trigger frame which aside from serving as a synchronization mechanism, also informs stations which resource units are allowed for random access. Using the trigger frame information, the stations engage in an OFDMA backoff process to win access to a resource unit. Similar to slotted ALOHA, the maximum normalized throughput of UORA is only 37 percent due to high probability of collisions at high loads. To reduce collisions, we equip UORA with carrier sensing capability resulting in a new uplink hybrid UORA (H-UORA) OFDMA access mechanism. Unlike other multi-carrier CSMA methods previously proposed in literature, H-UORA is an easily implementable modification to current 802.11ax WLANs. We show that H-UORA can achieve a normalized throughput of at least 80 percent (which increases further depending on the buffering capabilities of the access point) using various numerical analysis and simulations.

In this paper, we propose an Interleave-Division Multiple Access (IDMA) based uplink multi-user system fornext generation WLAN. By minimizing the latency throughaccurate detection per iteration, we were able to design a receiver architecture that meets the latency demands of current IEEE802.11 WLAN. To do this, the proposed system utilizes a novel algorithm for simplified LLR calculation of the soft input soft output demapper needed in the IDMA first stage detection.The proposed system has a maximum of 34.8 bits/s/Hz spectral efficiency for a single spatial stream and can support up to 8 users in a single 20MHz channel. We compare the proposed system to a reference OFDMA system and show its advantages in terms of diversity, flexibility and BER performance. Keywords: 802.11ax; IDMA; uplink multi-user access

In this paper, we propose a system that verifies and corrects the accuracy of symbol timing synchronization processing to determine reception time in Wi-Fi system. Time-of-flight (ToF) based Wi-Fi indoor mobile position estimation uses transmission and reception time stamp of radio waves between the mobile terminal targeted for estimation and fixed Wi-Fi receivers. However, it is known that the accuracy of radio reception time stamp in existing Wi-Fi receivers may be deteriorated due to the influence of multipath environment. Therefore, this paper proposes a system that corrects the accuracy of symbol timing synchronization processing that determines the reception time of radio wave in Wi-Fi system. This will improve the estimation accuracy of Wi-Fi indoor mobile position estimation.

This paper proposes a fast and low-complexity retransmission scheme for Industrial WLAN system. The proposed scheme exploits the frequency diversity and employs channel selectivity in order to achieve high-reliability and low-latency communication. The channel selectivity is carried out instantly by re-scheduling sub-carrier allocation during OFDM transmission in order to obtain diversity gain. Evaluation results show that the performance of the proposed scheme in terms of system-error rate and achievable transmission throughput rate, are significantly improved from the conventional re-transmission scheme. Furthermore, the proposed method only need a minor modification in both of communication protocol and transceiver design from the existing Industrial WLAN system. Hence, the low-complexity transmission scheme could be realized in current OFDM-based wireless system.