  Thanks to its simplicity and cost efficiency, wireless local area network
(WLAN) enjoys unique advantages in providing high-speed and low-cost wireless
services in hot spots and indoor environments. Traditional WLAN
medium-access-control (MAC) protocols assume that only one station can transmit
at a time: simultaneous transmissions of more than one station cause the
destruction of all packets involved. By exploiting recent advances in PHY-layer
multiuser detection (MUD) techniques, it is possible for a receiver to receive
multiple packets simultaneously. This paper argues that such multipacket
reception (MPR) capability can greatly enhance the capacity of future WLANs. In
addition, the paper provides the MAC-layer and PHY-layer designs needed to
achieve the improved capacity. First, to demonstrate MPR as a powerful
capacity-enhancement technique, we prove a "super-linearity" result, which
states that the system throughput per unit cost increases as the MPR capability
increases. Second, we show that the commonly deployed binary exponential
backoff (BEB) algorithm in today's WLAN MAC may not be optimal in an MPR
system, and that the optimal backoff factor increases with the MPR capability,
the number of packets that can be received simultaneously. Third, based on the
above insights, we design a joint MAC-PHY layer protocol for an IEEE
802.11-like WLAN that incorporates advanced PHY-layer signal processing
techniques to implement MPR.
