Esmael H. Dinan and Bijan Jabbari, Spreading Codes for Direct Sequence CDMA and Wideband CDMA Cellular Networks, IEEE Communications Magazine,vol.36,no. 9, pp. 4854, September #998.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....performance, due to the worst mean correlation characteristics for this type of sequence. Alternatively, groups of extended sequences, like as Kasami VL, have better correlation properties than groups of PN sequences and simultaneously they make available a huge number of spreading sequences [ 11 ]. II. SYSTEM MODEL Considering an MC multirate scheme, it is assumed that all of the K users have the same chip rate, Rc and they use the same bandwidth. For the generic k th user, Rk and Ebk denote data rate and its bit s energy respectively; the processing gain is constant and equal for all ....

E. H. Dinan and B. Jabbari, "Spreading codes for direct sequence CDMA and wideband CDMA cellular networks," IEEE Communications Magazine, vol. 36, pp. 48-54, Sept. 1998.

....SBCMACI and RLS beamspace time algorithms in sections IV and V; simulation results in section VI and finally, conclusion remarks in section VII. 0 7803 7589 0 02 17.00 2002 IEEE PIMRC 2002 II. SYSTEM MODEL We consider the reverse link of an asynchronous DS CDMA system employing complex spreading [10] and QPSK data modulation to reduce peak average ratio and achieve better bandwidth occupation. There are M users in the system and each user may transmit N b data symbols per packet over assumed stationary conditions. It is also assumed that the receiver employs an antenna array consisting of A ....

E. H. Dinan and B. Jabbai, "Spreading Codes for Direct Sequence CDMA and Wideband CDMA Cellular Networks", IEEE Comm. Mag., pp.48-54, Sep. 1998.

....s2 2 . s2] All sequences are assumed to belong to 1 N, 1 N) N. All orthonormal sequences can be grouped together into the signature matrix S = S1 I S2 ] The two orthonormal bases of the O O system can be constructed by assigning all Walsh Hadamard vectors wHi(N) i = l . N) of length N [8] to the setl users, and the same vectors, overlaid by a scrambling vector A = A1 . AN 1, 1 s, to the set2 users. This is actually 0 7803 7589 0 02 17.00 2002 IEEE PIMRC 2002 inspired by the principle of downlink separation between different cells in wideband CDMA [8] where downlink ....

..... N) of length N [8] to the setl users, and the same vectors, overlaid by a scrambling vector A = A1 . AN 1, 1 s, to the set2 users. This is actually 0 7803 7589 0 02 17.00 2002 IEEE PIMRC 2002 inspired by the principle of downlink separation between different cells in wideband CDMA [8], where downlink sequences of different cells are composed of the same orthogonal sequences, but overlaid by different scrambling sequences. Note that this construction puts a restriction on S2, since in this case S1 and S2 are related by diagonal matrix =diag A1 . As : S 2 = S (1) A ....

E. H. Dinan and B. Jabbad, "Spreading Codes for Direct Sequence CDMA and Wideband CDMA Cellular Networks," IEEE Commun. Mag.,pp 48-54, Sept. 1998.

....It is well known that the successful application of CDMA requires the availability of large number of spreading sequences having minimum cross correlation and capable of supporting variable data rates and large number of users with good bandwidth efficiency. Using multiple spreading scheme[2][3] the system deployment becomes flexible. Further use of complex scrambling[9] results in reduced envelope variations and high amplifier efficiency. However, this requires orthogonal non PN spreading codes (Walsh codes) to provide waveform orthogonality among all users and long PN spreading ....

....autocorrelation and cross correlation values of these codes which are of particular importance. A family of spreading codes (orthogonal codes) with ideal (i.e. zero valued cross correlation at all shifts) cross correlation properties results in zero multiple access interference. An orthogonal code [2] satisfies the following condition: 1 0 ; 0 ) k j j i k k where i and j are i and j members of an orthogonal code set; M: length of code and is the symbol duration. Normally, the number of uncorrelated sequences each of length M, is also M for the orthogonal ....

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. Esmael H. Dinan & Bijan Jabbari,Spreading Codes for Direct Sequence CDMA and wideband

....key feature of which is their low cross correlation properties. Specific code groups have already been selected for UMTS. OVSF, Gold, Kasami and Gold like codes are to be used for 6 the spreading, downlink and uplink scrambling codes and pilot codes respectively. These are defined in detail in [29, 30]. 31, 32] provide more information about the code families. Quadrature phase shift keying (QPSK) is the data modulation technique used. This technique effectively provides two mutually orthogonal binary phase shift keying (BPSK) data streams on I and Q branches. As the coding sequences used on ....

Esmael H. Dinan and Bjian Jabbari, "Spreading Codes for Direct Sequence CDMA and Wideband CDMA Cellular Networks", IEEE Communications Magazine, pp. 48--54, September 1998.

....resistance properties of Gold and other scrambling codes are evaluated in [22] The choice of the spreading code is very important, as it is the basic building block of any CDMA system. Many families of spreading codes, with satisfactory auto and cross correlation properties, exist[18] 19] [23]. In the actual systems, the processing gain is usually much larger than four, the value that was used in the previous examples. A large processing gain is, of course, highly beneficial in suppressing interference. For instance, the chip rate of WCDMA is 3.84 Mcps, which allows large spreading. ....

Dinan E.H. and Jabbari B., Spreading codes for direct sequence CDMA and Wideband CDMA cellular networks, IEEE Communications Magazine, September 1998, Vol. 3, No. 9, pp. 48-54.

....PN spreading sequences to different users whether they are located in the same cell or in different cells and use the same frequency in all cells. We do not address the issue of generating uncorrelated PN sequences for different users, a subject that is well documented in the technical literature [6]. Contrary to the cellular OCDMA outlined in the previous subsection, this scheme does offer the feature of eased network planning, but with respect to the single cell case, users in this scheme are also subject to intercell interference. More specifically, each user interferes with all other ....

E. H. Dinan, and B. Jabbari. Spreading Codes for Direct Sequence CDMA and Wideband CDMA Cellular Networks. IEEE Communications Magazine. Vol. 36. No. 9. Pages 48-54. September 1998.

....corresponding to one power control period. Within each slot, the DPDCH and DPCCH are transmitted in parallel on the in phase (I) and quadrature (Q) branches, respectively, using different codes. Short orthogonal codes are called channelization codes, long PN sequences are called scrambling codes [12]. Spreading and modulation of the uplink dedicated channels is shown in Figure 2. The spreading factors for the DPDCH and DPCCH can vary between 4 256, SF = 256=2 k ; k = 0; 1; Delta Delta Delta ; 6, carrying 10 Theta 2 k bits per slot each. Slot 1 Slot i Slot 16 TPC (TFI) Pilot Data ....

E. Dinan and B. Jabbari. Spreading codes for direct sequence cdma and wideband cdma cellular networks. IEEE Communications Magazine, September 1998.

....of such segments of the long spreading code resemble those of randomly selected sequences. Long code CDMA is therefore also referred to as random code CDMA. The wideband CDMA proposals for third generation cellular mobile communication, as well as IS 95, are all based on long code CDMA [1] [2], 3] By selecting mutually orthogonal codes for all users, the conventional matched filter detector achieves single user performance for each user. It is however not possible to maintain orthogonality in a mobile environment, hence the multiple access interference (MAI) that results may degrade ....

E. H. Dinan and B. Jabbari, "Spreading codes for direct sequence CDMA and wideband CDMA cellular networks," IEEE Communication Magazine, vol. 36, pp. 48--54, Sept. 1998.

....The DPDCH and DPCCH are time multiplexed. The number of chips per slot equals N cps . Moreover, Nk;P dedicated pilot symbols are broadcasted at the beginning of each DPCCH slot. For simplicity, we assume Qk = Qk;D = Qk;C 8 k. 3 Downlink Signal Model An extensive overview of WCDMA is given in [6, 5]. WCDMA has two types of dedicated physical channels, the dedicated physical control channel (DPCCH) and the dedicated physical data channel (DPDCH) On the downlink, the DPDCH and DPCCH are time multiplexed, cf. Figure 2. In case of data rates not exceeding 2 Mb s, one connection consists of one ....

E. H. Dinan and B. Jabbari, "Spreading codes for direct sequence CDMA and wideband CDMA cellular networks", IEEE Communication Magazine, vol. 36, pp. 48--54, Sept. 1998.

.... one alternative to choose v i to encode the message b is to consider an m sequence v 1 and for each i, v i 1 results from v i by a circular shift of length 1 (each element of v i is shifted to right and the last element becomes the first) An other alternative for v i is to use Gold Codes [11,3]. A family of Gold Codes is obtained using an m sequence v 1 and a q decimation of it. The decimation v 0 1 is obtained by sampling every q th element of v 1 . Note that v 0 1 has period N if and only if gcd(N ,q) 1, where gcd denotes the greatest common divisor. Each element v i 1 of the ....

E. H. Dinan and B. Jabbari. Spreading codes for direct sequence CDMA and wideband CDMA cellular network. IEEE Communications Magazine, June 1998.

....synchronized, orthogonal codes, C ok ; k = 1; 2; Delta Delta Delta ; K, are used to separate the channels. These channels are then linearly combined (summed) and spread (multiplied) by a transmitter specific scramble code C s . In UMTS IMT 2000, OVSF (orthogonal variable spreading factor) codes [13] are used as orthogonal codes which allow a constant spread bandwidth for various information rates, and Gold codes or large Kasami code sets are used as scramble codes. For downlink, every base station uses the same set of OVSF codes as its channelization codes, but each base station uses a ....

E.H. Dinan and B. Jabbari, "Spreading Codes for Direct Sequence CDMA and Wideband CDMA Cellular Networks," IEEE Com. Mag., pp.48--54, Sept. 1998. 17

....in CODIT, and the North American 1.9 GHz PCS are shown in Appendices A, B and C, respectively. It must be noted that UMTS IMT 2000 is only a possible solution to the 3G mobile communications. The standardization of W CDMA is still underway, and different proposals are under investigation [DinanE 98, p.53] 6 Chapter 2 Physical Layer 2.1 CDMA and Multiple Spreading 2.1.1 Orthogonal spreading It is well known [PickhR 82, p.856] that in CDMA, if the spreading signals, OE i (t) 2 L 2 (T ) i = 1; 2; Delta Delta Delta ; M , are orthogonal, i.e. Z T 0 OE k (t)OE l (t) dt = ffi kl ....

....the wanted signal, say x i , is theoretically zero after despreading, i.e. I ij = Z T 0 x j OE j (t)OE i (t) dt = x j Z T 0 OE j (t)OE i (t) dt = 0; i 6= j (2.2) It is not very difficult to design a set of orthogonal signals or codes. Some good examples are Hadamard Walsh codes [AdachF 97] DinanE 98] see A.4 for details. However, when these codes are mis aligned, the crosscorrelation of these codes will be non zero or even be one (1) that is, they are no longer orthogonal. This is quite natural if we look at FDMA (frequency division multiple access) and TDMA (time division multiple ....

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E.H. Dinan and B. Jabbari, Spreading Codes for Direct Sequence CDMA and Wideband CDMA Cellular Networks, IEEE Com. Mag., Sept. 1998, pp.48-54.

....the specific choice of method for generating the pseudo random sequence has direct implications to the reliability and security of the embedded mark. Pseudo random number generators described in watermarking literature include msequences, Gold Codes, Kasami codes, Legendre sequences, perfect maps [4, 16] and also two or higher dimensional arrays [16] in place of the one dimensional pseudo random vectors. 2.1.1 m sequences and Gold Codes It is shown in [11] how pseudo random sequences can be used to spread the signal spectrum. In order to despread the signal these pseudo random sequences need to ....

....to choose v i to encode the message b (section 2. 1) is to consider an m sequence v 1 and for each i, v i 1 results from v i by a circular shift of length 1 (each element of v i is shifted to right and the last element becomes the first) An other alternative for v i is to use Gold Codes [11, 4]. A family of Gold Codes is obtained using an m sequence v 1 and a q decimation of it. The decimation v 0 1 is obtained by sampling every q th element of v 1 . Note that v 0 1 has period N if and only if gcd(N ,q) 1, where gcd denotes the greatest common divisor. Each element v i 1 of the ....

[Article contains additional citation context not shown here]

E. H. Dinan and B. Jabbari. Spreading codes for direct sequence CDMA and wideband CDMA cellular network. IEEE Communications Magazine, June 1998.

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Esmael H. Dinan and Bijan Jabbari, Spreading Codes for Direct Sequence CDMA and Wideband CDMA Cellular Networks, IEEE Communications Magazine,vol.36,no. 9, pp. 4854, September #998.

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E.H. Dinan and B. Jabbari, "Spreading codes for direct sequence cdma and wideband cdma cellular networks," in IEEE Communications Magazine, pp. 48--54. September 1998.

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E.H. Dinan and B. Jabbari, "Spreading Codes for Direct Sequence CDMA and Wideband CDMA Cellular Networks," IEEE Communications Magazine, vol. 36, September 1998, pp. 48-54.

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Dinan, E. H., and Jabbari, B., "Spreading Codes for Direct Sequence CDMA and Wideband CDMA Cellular Networks," IEEE Communications Magazine, Sept. 1998, pp 48-54

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E. H. Dinan and B. Jabbari. Spreading codes for direct sequence CDMA and wideband CDMA cellular network. IEEE Communications Magazine, pages 48--54, June 1998.

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E. H. Dinan and B. Jabbari, "Spreading codes for direct sequence CDMA and wideband CDMA cellular networks," IEEE Commun. Mag., vol. 36, pp. 48--54, Sept. 1998.

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E.H. Dinan and B. Jabbari. Spreading codes for direct sequence cdma and wideband CDMA cellular network. IEEE Communications Magazine, June 1998.

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