无线体域网低复杂度重复码解扩频方法研究

doi:10.11959/j.issn.1000-436x.2015207

摘要/Abstract

摘要：

为了提高数据传输的可靠性，降低窄带接收机的复杂度，无线体域网标准 IEEE 802.15.6 采用了基于重复码的扩频方法。通过设计一种根据动态阈值选择性进行量度运算的解扩频结构，并结合硬判决阈值特性利用简化的最大比合并以及广义最小距离原理，提出了硬阈值—合并法和硬阈值—删除法，计算复杂度较小，同时解扩频性能近似最优。理论分析及仿真结果表明，与基于最大似然方法的解扩频相比，其扩频增益接近理论值，在高信噪比环境下，计算复杂度可降低86%以上。

关键词: 解扩频, 重复码, 软判决, 低复杂度, 无线体域网

Abstract:

To improve the reliability of data transmission and reduce the complexity of the narrow band receiver for wireless body area networks(WBAN),spreading with repetition code is used in IEEE 802.15.6 standard.A despreading structure in which the metrics of reliability were calculated selectively according to the dynamic threshold was designed.Combined with hard decision,hard threshold-combine and hard threshold-delete despreading methods by simplifying maximal ratio combining and generalized minimum distance principle respectively were proposed,which had low complexity and near-optimal performance.The theoretical analysis and simulation results show that compared to despreading based on maximum likelihood method,the spreading gain of the proposed methods is close to the theoretical value and the computational complexity can be reduced by 86% at most under high SNR circumstances.

Key words: despreading, repetition code, soft-decision, low-complexity, wireless body area networks

迟宇,陈岚,吕超. 无线体域网低复杂度重复码解扩频方法研究[J]. 通信学报, 2015, 36(8): 146-152.

Yu CHI,Lan CHEN,Chao LV. Low-complexity despreading scheme with repetition code for wireless body area networks[J]. Journal on Communications, 2015, 36(8): 146-152.

图/表 14

图1

图2

图3

图4

表1

图2中各部分模块产生的运算量"

模块	运算量	单位	运算类型
解调硬判决	N	O(1)	比较
解扰	N	O(1)	异或
解交织及硬判决解扩频	$\frac{N (F - 1)}{F}$	O(1)	比较
总计	$3 N - \frac{N}{F}$	O(1)

表1

表2

图3中各部分模块产生的运算量"

模块	运算量	单位	运算类型
解扰	$N + \frac{2 k N}{2}$	O(1)	比较+取相反数运算
解交织及量度合并	$\frac{N (F - 1)}{F}$	O(k)	k bit加法
解扩频硬判决	$\frac{N}{F}$	O(1)	比较
总计	$3 k N + \frac{2 N (1 - k)}{F}$	O(1)

表2

表3

图4中硬阈值—合并法各部分模块产生的运算量"

模块	运算量	单位	运算类型
硬判决分支解调	N	O(1)	比较
硬判决分支解扰	N	O(1)	异或
硬判决分支解扩频	N	O(1)	比较
软判决分支解扰	$F T + \frac{2 k F T}{2}$	O(1)	比较+取相反数运算
软判决分支量度合并	T(F?1)	O(k)	k bit加法
软判决分支解扩频	T	O(1)	比较
总计	3N+3kFT+2T(1?k)	O(1)

表3

表4

图4中硬阈值—删除法各部分模块产生的运算量"

模块	运算量	单位	运算类型
硬判决分支解调	N	O(1)	比较
硬判决分支解扰	N	O(1)	异或
硬判决分支解扩频	N	O(1)	比较
软判决分支解扰	$F T + \frac{2 k F T}{2}$	O(1)	比较+取相反数运算
删除x个符号	$\frac{F T}{4 k} + \frac{k}{2 \sum_{l = 1}^{T} \sum_{i = 1}^{x} (F - i)}$	O(1)	取绝对值+比较
软判决分支解扩频	$\sum_{l = 1}^{T} (F - x)$	O(1)	比较
总计	$3 N + (2 k + 1) F T + \frac{k}{2 \sum_{l = 1}^{T} \sum_{i = 1}^{x} (F - i) + \sum_{l = 1}^{T} (F - x)}$	O(1)

表4

表5

仿真参数设置"

各模块	仿真参数
调制方式	$\frac{π}{２} - DBPSK$
解调方式	差分解调
负载长度	255 byte
信道环境	高斯白噪声
交织函数	$b (i) = a [F \cdot r e m (i, 2) + ⌊ \frac{i}{2} ⌋] i = 0, 1, \dots, 2 F - 1$
加扰多项式	G(x)=1+x²+x¹²+x¹³+x¹⁴

表5

图5

图6

图7

图8

图9

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