一种新的大容量的二维光正交码

构造了一种扩展的双曲线性同余码(EHLC)并分析了其码字性能.用该码作为时间扩频伪随机序列和以素数码(PC)作为波长跳频伪随机序列,再构成一种新的二维光正交码EHLC/PC.然后分析了EHLC/PC码字的性能,并与EQC/PC作了比较.相比之下,前者的互相关性能略有下降,但码字容量大大增加.因此,EHLC/PC适合于用户数较多的OCDMA系统.

A NEW FAMILY OF TWO-DIMENSIONAL OPTICAL ORTHOGONAL CODES FOR MASSIVE OPTICAL CDMA NETWORKS

A new one dimensional optical orthogonal codes(1 D OOC) named extended hyperbolic line congruence codes(EHLC) is constructed,and its performance is analyzed.Compared with extended quadratic congruence codes(EQC),EHLC has large code cardinality,but has a little poor performances of auto correlation and cross correlation.Then,using EHLC for time spreading and prime sequence(PC) for wavelength hopping,a new two dimensional optical orthogonal codes(2 D OOC)named EHLC/PC is constructed.Because the code weight of EHLC equals(p 1) and the code weight of PC equals p,selection function f(i) should be used to pick out(p 1)wavelengths from each prime sequence.At last,the performance of EHLC/PC is analyzed,and is also compared with EQC/PC.Because each wavelength within a code is different,auto correlation of EHLC/PC equals zero.When examining the cross correlation of EHLC/PC,authors should consider four different modes:same time spreading pattern/same wavelength hopping pattern(different s k),same time spreading pattern/different wavelength hopping pattern,different time spreading pattern/same wavelength hopping pattern,different time spreading pattern/different wavelenght hopping pattern.By using difference function and wavelength hopping pattern,it is not difficult to get the cross correlation performances of EHLC/PC.It is shown that the cross correlation performance of EHLC/PC is a little worse than EQC/PC,but EHLC/PC has much larger code cardinality.Moreover,EHLC/PC has shorter code length and smaller code weight,which can enhance user data rate and also can reduce the complexity of optical encoders/decoders.Therefore,EHLC/PC is suitable for massive optical code division multiple access(OCDMA) networks.