认知无线电系统资源分配策略
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"这篇资源是关于资源分配的，具体是一篇发表在IEEE Transactions on Communications期刊上的文献，适合通信领域的研究者参考。文章主要探讨了协作多用户正交频分复用(MU-OFDM)认知无线电(CR)系统中的资源分配策略。"
在3204页，这篇2011年11月出版的IEEE文献提出了一个联合子载波和功率分配算法，用于协作型多用户OFDM基的认知无线电系统。作者Chiuan-Hsu Chen、Chin-Liang Wang和Chih-Tsung Chen通过将三节点中继网络简化为具有等效信道增益的两节点网络，构建了一个与非协作型MU-OFDM CR系统相似的资源分配问题模型。
论文的抽象部分指出，该资源分配问题的解决方法是在给定功率分布下进行子载波分配操作，其中最大容量优化在子载波和功率之间交替进行，形成一种联合子载波和功率分配算法。为了降低高复杂度的最优功率分配算法（例如，迭代分割水填算法）的计算复杂性，研究人员进一步开发了一种简化方法。
资源分配在无线通信系统中起着至关重要的作用，因为它直接影响系统的性能和效率。在认知无线电系统中，尤其如此，因为这种系统需要动态地调整资源以适应环境变化，同时避免对授权用户的干扰。协同多用户设置增加了复杂性，因为多个用户必须协同工作，共享资源以提高整体系统性能。
本文提出的方法可能包括以下几个关键点：
1. 等效信道建模：通过将复杂的三节点中继网络模型简化为两节点模型，可以更容易地处理资源分配问题，这降低了理论分析和算法设计的难度。
2. 联合分配策略：通过交替优化子载波分配和功率分配，可以同时考虑这两个因素对系统性能的影响，以实现最佳的资源利用。
3. 简化算法：对于联合方案的高复杂度最优功率分配算法，文章可能介绍了一种更高效的近似算法，这有助于在实际系统中实现这些策略。
4. 性能优化：目标可能是最大化系统容量，同时确保对主用户的保护，这通常涉及到在干扰限制下的资源分配优化。
5. 应用与影响：这样的资源分配策略可以应用于未来智能网络，如5G或6G，以提升频谱效率，支持更多的连接设备，并优化用户体验。
这篇文献为通信领域提供了一种新的视角和方法来解决协作多用户认知无线电系统中的资源分配挑战，对于深入理解认知无线电和优化无线通信网络性能的研究人员来说，这是一个宝贵的参考资料。
3206 IEEE TRANSACTIONS ON COMMUNICATIONS, VOL. 59, NO. 11, NOVEMBER 2011
,, ,,
,
eq k n eq k n
hp
,,
,
kk kk
sr n sr n
hp
,,
,
kk
rdn rdn
hp
,,
,
kk
sdn sdn
hp
k
θ
k
sd
d
kk
sr
d
k
rd
d
k
sd
d
Fig. 2. (a) A three-node relay network. (b) An equivalent two-node network.
and 𝛽 may vary for each link, it is assumed that they are not
changed for all communication links. The entire operation of
the three-node relay network is as follows: in phase 1, the
source transmits messages with variance 𝑝
𝑠
𝑘
𝑟
𝑘
,𝑛
to the relay
and messages with variance 𝑝
𝑠
𝑘
𝑑,𝑛
to the destination; in phase
2, the relay transmits messages with variance 𝑝
𝑟
𝑘
𝑑,𝑛
to the
destination.
Assume that 𝑝
𝑠
𝑘
𝑟
𝑘
,𝑛
= 𝑝
𝑠
𝑘
𝑑,𝑛
, the relay node uses the DF
scheme as the cooperative strategy, the noise power of each
link is independent identically distributed (i.i.d.) circularly
symmetric additive white Gaussian noise (AWGN) with unity
variance, and the destination combines the received signals
from the source node in phase 1 and the relay node in phase 2
through the maximal ratio combining. When we assume that
𝑠
𝑘
-𝑟
𝑘
transmission is successful for the entire DF process,
the optimal power allocation problem to maximize the overall
error-free capacity at the destination is given by
max
𝑝
𝑠
𝑘
𝑑,𝑛
,𝑝
𝑟
𝑘
𝑑,𝑛
1
2
log
2
(1 + min{∣ℎ
𝑠
𝑘
𝑑,𝑛
∣
2
𝑝
𝑠
𝑘
𝑑,𝑛
+
∣ℎ
𝑟
𝑘
𝑑,𝑛
∣
2
𝑝
𝑟
𝑘
𝑑,𝑛
, ∣ℎ
𝑠
𝑘
𝑟
𝑘
,𝑛
∣
2
𝑝
𝑠
𝑘
𝑟
𝑘
,𝑛
})
subject to
𝑝
𝑠
𝑘
𝑑,𝑛
+ 𝑝
𝑟
𝑘
𝑑,𝑛
2
= 𝑝
𝑠
𝑘
,𝑛
(1)
where the average of the transmit power of the source node
(𝑝
𝑠
𝑘
𝑑,𝑛
) and that of the relay node (𝑝
𝑟
𝑘
𝑑,𝑛
) is constrained to
be 𝑝
𝑠
𝑘
,𝑛
, which is the allocated power on subcarrier 𝑛 at the
source node for direct transmission. Note that it is necessary
to put this power constraint on (1) such that we can make
a fair performance comparison (under equal transmit power)
between the cooperative approach and the direct transmission
scheme. The factor 1/2 in (1) results from the fact that the
signal is transmitted over two time slots (or two phases) in the
cooperative scheme. From [17], the solution to this problem
is
𝑝
𝑠
𝑘
𝑑,𝑛
= 𝑝
𝑠
𝑘
𝑟
𝑘
,𝑛
=
∣ℎ
𝑟
𝑘
𝑑,𝑛
∣
2
∣ℎ
𝑠
𝑘
𝑟
𝑘
,𝑛
∣
2
+ ∣ℎ
𝑟
𝑘
𝑑,𝑛
∣
2
−∣ℎ
𝑠
𝑘
𝑑,𝑛
∣
2
𝑝
𝑒𝑞,𝑘,𝑛
and 𝑝
𝑟
𝑘
𝑑,𝑛
=
∣ℎ
𝑠
𝑘
𝑟
𝑘
,𝑛
∣
2
−∣ℎ
𝑠
𝑘
𝑑,𝑛
∣
2
∣ℎ
𝑠
𝑘
𝑟
𝑘
,𝑛
∣
2
+ ∣ℎ
𝑟
𝑘
𝑑,𝑛
∣
2
−∣ℎ
𝑠
𝑘
𝑑,𝑛
∣
2
𝑝
𝑒𝑞,𝑘,𝑛
(2)
when ∣ℎ
𝑠
𝑘
𝑑,𝑛
∣
2
≤∣ℎ
𝑠
𝑘
𝑟
𝑘
,𝑛
∣
2
and ∣ℎ
𝑠
𝑘
𝑑,𝑛
∣
2
< ∣ℎ
𝑟
𝑘
𝑑,𝑛
∣
2
,where
𝑝
𝑒𝑞,𝑘,𝑛
=2𝑝
𝑠
𝑘
,𝑛
;if∣ℎ
𝑟
𝑘
𝑑,𝑛
∣
2
≤∣ℎ
𝑠
𝑘
𝑑,𝑛
∣
2
or ∣ℎ
𝑠
𝑘
𝑟
𝑘
,𝑛
∣
2
<
∣ℎ
𝑠
𝑘
𝑑,𝑛
∣
2
< ∣ℎ
𝑟
𝑘
𝑑,𝑛
∣
2
, 𝑝
𝑠
𝑘
𝑑,𝑛
= 𝑝
𝑠
𝑘
𝑟
𝑘
,𝑛
= 𝑝
𝑒𝑞,𝑘,𝑛
and
𝑝
𝑟
𝑘
𝑑,𝑛
=0. With the above definitions, the signal-to-noise
ratio (SNR) at the destination node is,
∣ℎ
𝑠
𝑘
𝑑,𝑛
∣
2
𝑝
𝑠
𝑘
𝑑,𝑛
+ ∣ℎ
𝑟
𝑘
𝑑,𝑛
∣
2
𝑝
𝑟
𝑘
𝑑,𝑛
=
∣ℎ
𝑠
𝑘
𝑟
𝑘
,𝑛
∣
2
∣ℎ
𝑟
𝑘
𝑑,𝑛
∣
2
𝑝
𝑒𝑞,𝑘,𝑛
∣ℎ
𝑠
𝑘
𝑟
𝑘
,𝑛
∣
2
+∣ℎ
𝑟
𝑘
𝑑,𝑛
∣
2
−∣ℎ
𝑠
𝑘
𝑑,𝑛
∣
2
, ∣ℎ
𝑠
𝑘
𝑑,𝑛
∣
2
≤∣ℎ
𝑠
𝑘
𝑟
𝑘
,𝑛
∣
2
and ∣ℎ
𝑠
𝑘
𝑑,𝑛
∣
2
< ∣ℎ
𝑟
𝑘
𝑑,𝑛
∣
2
∣ℎ
𝑠
𝑘
𝑑,𝑛
∣
2
𝑝
𝑒𝑞,𝑘,𝑛
, otherwise
≜ ℎ
2
𝑒𝑞,𝑘,𝑛
𝑝
𝑒𝑞,𝑘,𝑛
(3)
where ℎ
2
𝑒𝑞,𝑘,𝑛
= ∣ℎ
𝑠
𝑘
𝑟
𝑘
,𝑛
∣
2
∣ℎ
𝑟
𝑘
𝑑,𝑛
∣
2
/(∣ℎ
𝑠
𝑘
𝑟
𝑘
,𝑛
∣
2
+ ∣ℎ
𝑟
𝑘
𝑑,𝑛
∣
2
−
∣ℎ
𝑠
𝑘
𝑑,𝑛
∣
2
) if ∣ℎ
𝑠
𝑘
𝑑,𝑛
∣
2
≤∣ℎ
𝑠
𝑘
𝑟
𝑘
,𝑛
∣
2
and ∣ℎ
𝑠
𝑘
𝑑,𝑛
∣
2
< ∣ℎ
𝑟
𝑘
𝑑,𝑛
∣
2
;
otherwise, ℎ
2
𝑒𝑞,𝑘,𝑛
= ∣ℎ
𝑠
𝑘
𝑑,𝑛
∣
2
. With (3), the three-node
network can be simplified to an equivalent two-node network
with the corresponding channel gain ℎ
𝑒𝑞,𝑘,𝑛
and power 𝑝
𝑒𝑞,𝑘,𝑛
,
as shown in Fig. 2(b). Assume that 𝜍
𝑘
= 𝑑
𝑟
𝑘
𝑑
/𝑑
𝑠
𝑘
𝑟
𝑘
and
𝐺
𝑠,𝑘
=(𝑑
𝑠
𝑘
𝑑
/𝑑
𝑠
𝑘
𝑟
𝑘
)
𝛽
=(1+𝜍
2
𝑘
− 2𝜍
𝑘
cos 𝜃
𝑘
)
𝛽/2
is the
geometrical gain achieved by the proximity advantage of the
relay node over the destination node [18]. When 𝑠
𝑘
-𝑟
𝑘
and
𝑟
𝑘
-𝑑 links are better than 𝑠
𝑘
-𝑑, ℎ
2
𝑒𝑞,𝑘,𝑛
in (3) can be rewritten
as
ℎ
2
𝑒𝑞,𝑘,𝑛
=
∣ℎ
𝑠
𝑘
𝑟
𝑘
,𝑛
∣
2
∣ℎ
𝑟
𝑘
𝑑,𝑛
∣
2
∣ℎ
𝑠
𝑘
𝑟
𝑘
,𝑛
∣
2
+ ∣ℎ
𝑟
𝑘
𝑑,𝑛
∣
2
−∣ℎ
𝑠
𝑘
𝑑,𝑛
∣
2
=
𝐿∣𝑔
𝑠
𝑘
𝑟
𝑘
,𝑛
∣
2
𝑑
−𝛽
𝑠
𝑘
𝑟
𝑘
∣𝑔
𝑟
𝑘
𝑑,𝑛
∣
2
𝑑
−𝛽
𝑟
𝑘
𝑑
∣𝑔
𝑠
𝑘
𝑟
𝑘
,𝑛
∣
2
𝑑
−𝛽
𝑠
𝑘
𝑟
𝑘
+ ∣𝑔
𝑟
𝑘
𝑑,𝑛
∣
2
𝑑
−𝛽
𝑟
𝑘
𝑑
−∣𝑔
𝑠
𝑘
𝑑,𝑛
∣
2
𝑑
−𝛽
𝑠
𝑘
𝑑
=
𝐿∣𝑔
𝑠
𝑘
𝑟
𝑘
,𝑛
∣
2
∣𝑔
𝑟
𝑘
𝑑,𝑛
∣
2
𝐺
𝑠,𝑘
𝑑
−𝛽
𝑟
𝑘
𝑑
∣𝑔
𝑠
𝑘
𝑟
𝑘
,𝑛
∣
2
𝑑
−𝛽
𝑠
𝑘
𝑟
𝑘
+ ∣𝑔
𝑟
𝑘
𝑑,𝑛
∣
2
𝑑
−𝛽
𝑟
𝑘
𝑑
−∣𝑔
𝑠
𝑘
𝑑,𝑛
∣
2
𝑑
−𝛽
𝑠
𝑘
𝑑
𝑑
−𝛽
𝑠
𝑘
𝑑
= 𝐿
∣𝑔
𝑠
𝑘
𝑟
𝑘
,𝑛
∣
2
∣𝑔
𝑟
𝑘
𝑑,𝑛
∣
2
𝐺
𝑠,𝑘
∣𝑔
𝑠
𝑘
𝑟
𝑘
,𝑛
∣
2
𝜍
𝛽
𝑘
+ ∣𝑔
𝑟
𝑘
𝑑,𝑛
∣
2
−∣𝑔
𝑠
𝑘
𝑑,𝑛
∣
2
𝜍
𝛽
𝑘
/𝐺
𝑠,𝑘
𝑑
−𝛽
𝑠
𝑘
𝑑
,
∣𝑔
𝑠
𝑘
𝑑,𝑛
∣
2
≤∣𝑔
𝑠
𝑘
𝑟
𝑘
,𝑛
∣
2
𝐺
𝑠,𝑘
and ∣𝑔
𝑠
𝑘
𝑑,𝑛
∣
2
< ∣𝑔
𝑟
𝑘
𝑑,𝑛
∣
2
𝐺
𝑠,𝑘
𝜍
𝛽
𝑘
≜ 𝐿𝑔
2
𝑒𝑞,𝑘,𝑛
𝑑
−𝛽
𝑠
𝑘
𝑑
(4)
where 𝑔
2
𝑒𝑞,𝑘,𝑛
= ∣𝑔
𝑠
𝑘
𝑟
𝑘
,𝑛
∣
2
∣𝑔
𝑟
𝑘
𝑑,𝑛
∣
2
𝐺
𝑠,𝑘
/[∣𝑔
𝑠
𝑘
𝑟
𝑘
,𝑛
∣
2
𝜍
𝛽
𝑘
+
∣𝑔
𝑟
𝑘
𝑑,𝑛
∣
2
−∣𝑔
𝑠
𝑘
𝑑,𝑛
∣
2
𝜍
𝛽
𝑘
/𝐺
𝑠,𝑘
].
B. A Resource Allocation Problem for Cooperative MU-
OFDM CR Systems
In a CR system, the transmitted power of SUs may cause un-
expected interference to PUs, whether or not PUs are starting
communication on channels currently used by SUs. Thus, an
additional mechanism is needed to protect the communication
links of PUs so that the received signal-to-interference-plus-
noise ratio (SINR) on each PU is larger than a threshold [12],
[13]. By taking into account all PUs, we can modify the SINR
constraint on the power allocated for user 𝑠
𝑘
on subcarrier 𝑛
(i.e., 𝑝
𝑠
𝑘
,𝑛
) given by [12] as follows:
𝑝
𝑠
𝑘
,𝑛
≤ min
𝑢=1,2,...,𝑀
1
∣ℎ
𝑠
𝑘
,𝑢
∣
2
(
𝑃
𝑇
∣ℎ
0𝑢
∣
2
𝜁
−
𝑁
0
𝐵
𝑁
) ≜ 𝑃
𝑠
𝑘
,max
(5)
where 𝑃
𝑇
is the transmitted power of each PU, ∣ℎ
0𝑢
∣
2
is the
channel power gain of the link between the transmit PU and
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