PQ-MAC：利用对等节点队列信息优化全双工WLAN双向传输
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"PQ-MAC:全双工无线网络中的双向传输优化策略"
PQ-MAC是一项针对全双工（Full-Duplex, FD）无线局域网（WLAN）的创新多访问控制协议（Media Access Control, MAC）。传统的FD MAC在设计上往往未能充分利用双向通信的优势，主要原因是它们忽视了一个关键特性：建立双向传输的可行性取决于对等节点的队列状态。在无线环境中，由于信号干扰、碰撞等因素，对邻近设备的数据发送和接收必须在合适的时机进行，而这种时机与对等节点的实时数据流量密切相关。
PQ-MAC正是针对这一空白提出了一个创新思路，它首先捕捉到并利用了这一点，通过获取对等节点的排队信息，智能地管理双向传输的发起时机。这种设计允许PQ-MAC动态调整其通信策略，确保在对等节点的通信需求允许时进行双向数据交换，从而最大化网络的吞吐量和效率。相比于传统方法，PQ-MAC的实现引入了一定程度的控制开销，但这种开销被证明是合理的，因为它能够显著提升整体性能。
在设计上，PQ-MAC可能包括了以下几个关键组件：
1. 排队状态感知：PQ-MAC需要实时监控对等节点的输入/输出数据流，通过监听或请求邻居的队列长度信息，判断是否具备启动双向传输的条件。
2. 冲突避免与调度算法：基于排队信息，PQ-MAC会采用一种智能的冲突避免策略，如优先级调度或者公平性算法，以减少竞争和拥塞。
3. 动态切换机制：当一个节点的队列空闲或传输能力增强时，PQ-MAC会动态调整自己的通信模式，从单工切换到双向，反之亦然。
4. 轻量级协议扩展：为了最小化对原有协议栈的影响，PQ-MAC可能会采用一种增量式设计，只在必要的时候更新或扩展现有的MAC帧结构，以便处理双向传输的相关信息。
实验证明，在一个单个FD-WLAN小区中，PQ-MAC能够在保持适度的控制信息传递的同时，显著提高网络的整体性能。这意味着在高密度的无线环境和竞争激烈的通信场景下，PQ-MAC能够提供更高的数据传输速率和更低的时延，对于提高WLAN的吞吐量和用户体验具有重要意义。
总结来说，PQ-MAC通过巧妙地结合对等节点的排队信息，有效地发掘了全双工无线网络中潜在的双向传输机会，为提高WLAN性能提供了一种新的可能。尽管在实施过程中需要考虑一些额外的管理和协调工作，但考虑到性能提升的潜力，这项技术对于未来的无线通信系统具有深远影响。
PQ-MAC: Exploiting Bidirectional Transmission
Opportunities via Leveraging Peers’ Queuing
Information for Full-Duplex WLAN
Rongchang Duan
∗†
, Qinglin Zhao
‡
, Hanwen Zhang
∗†
, Yujun Zhang
∗†
and Zhongcheng Li
∗†
∗
University of Chinese Academy of Sciences, Beijing, P.R.China
†
Institute of Computing Technology, Chinese Academy of Sciences, Beijing, P.R.China
‡
Macau University of Science and Technology, Macau, P.R.China
Abstract—Full-duplex (FD) wireless is an attractive PHY
technology with high potential to improve the throughput of
WLAN due to bidirectional transmissions. However, existing FD
MACs fail to fully take advantage of bidirectional transmissions
because of neglecting a feature of FD wireless that whether to
build bidirectional transmissions relies on the queuing state of
peers. In this paper, we design PQ-MAC, the first FD MAC
which exploits more bidirectional transmission opportunities by
leveraging peers’ queuing information. Since PQ-MAC seizes
the neglected but important feature, PQ-MAC can improve the
performance with a slight transmission overhead. Simulations
show that, in a 1-cell FD WLAN, PQ-MAC can achieve higher
throughput than existing MACs when the buffer of AP is rela-
tively small (≤200 frames). When the buffer of AP is relatively
large (>200 frames), PQ-MAC can reduce the queuing delay
without the loss of throughput.
I. INTRODUCTION
Full-duplex (FD) wireless [1] is a very promising PHY-layer
technology that enables wireless nodes to transmit and receive
simultaneously, and therefore has attracted great attentions [2]
[3]. Despite significant progress on the PHY-layer develop-
ment, MAC-layer protocol should be carefully designed to
fully take advantage of FD gain.
The ability of building bidirectional transmissions is the key
reason of FD gain
1
. Yet, bidirectional transmissions cannot
always be built. The prerequisite of building a bidirectional
transmission between two FD nodes is called bidirectional
transmission opportunity which defines the state that the two
FD nodes buffer frames for each other at the same time. The
opportunities dynamically appear since the queuing state of
FD nodes dynamically changes. Thus, to fully take advantage
of FD gain, a well-designed MAC should exploit bidirectional
transmission opportunities as possible.
Commonly, a transmission between two FD nodes is initi-
ated by one side. The node which initiates the transmission
is called Primary Transmitter (PT), while the other node is
called Primary Receiver (PR). We define that PT and PR are
peers for each other throughout this paper. Using existing
FD MACs, PT just contends for the media based on local
information, but have no idea about the queuing information of
1
We focus on the FD WLANs in this paper and hence do not consider
3-node full-duplex transmissions, since the 3-node full-duplex transmissions
among nodes are uncommon in FD WLANs [11].
20 30 40 50 60 70 80 90 100
AP's buffer (client's buffer=50)
0.4
0.5
0.6
0.7
0.8
0.9
1.0
FD ratio (ratio of bi-transmissions)
Real FD ratio
Ideal FD ratio
Fig. 1: Ideal and real FD ratio of existing MACs in a 1-cell
FD WLAN with 1 FD AP and 20 pairs of FD clients, when
the buffer capacity of AP varies.
PR. When PT wins the contention and initiates a transmission,
only if PR has buffered frames for PT, PR would send a
frame back to PT and thus a bidirectional transmission is
built; otherwise, PT only transmits uni-directionally, losing
the benefit of bidirectional transmissions. Since the existing
MACs do not identify bidirectional transmission opportunities
before random contention, we say that the existing MACs
inadvertently capture bidirectional transmission opportu-
nities.
We compare the ideal FD ratio with the real FD ratio
2
of
existing MACs in an FD WLAN which consists of 1 FD access
point (AP) and 20 pairs of FD clients. In the network, each
client communicates with its partner via AP which buffers
some frames so as to build bidirectional transmissions. We
assume that clients are fully backlogged with frames for their
partners, so ideally all the transmissions can be bidirectional
transmissions. Fig.1 plots the FD ratio as the buffer capacity
of AP varies and it shows that existing MACs build an amount
of uni-directional transmissions. It is because, using existing
MACs, whether a client builds bidirectional transmissions after
random contention depends on the frames in AP’s buffer. Thus,
the more frames that AP buffers, the higher probability that
2
The FD ratio is calculated as the ratio of bidirectional transmissions in
total transmissions. All the existing MACs perform similarly in the network,
so that we plot one line to represent all of them.
2019 IEEE Symposium on Computers and Communications (ISCC)
978-1-7281-2999-0/19/$31.00 ©2019 IEEE
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