System for radio transmission of digital signals between a plurality of subscriber stations and base station
AssigneeSiemens Aktiengesellschaft
InventorsPeter Jung, Friedbert Berens, Paul-Walter Baier, Jörg Plechinger, Karl Kammerlander
Life of this patent
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Abstract
The new CDMA (Code Division Multiple Access) system structure which is equivalent to the structure of a CDMA system operating with direct code spread (DS, Direct Sequence) but operates with multicarrier (MC) methods. The multicarrier method is introduced a suitable selection of the spread code, with the result that the production of signals in CDMA systems with DS and with MC is harmonized and JD (Joint Detection) multisubscriber detection methods, which are known per se, with or without diversity reception can be used.
Claims31
A system for transmitting digital signals by radio between a plurality of subscriber stations and a base station using the so-called MC-CDMA (Multicarrier—Code Division Multiple Access) method in which a plurality of useful links are processed simultaneously in a common RF frequency band, comprising:
- data blocks of finite length, which can be represented by data vectors
- d(k)=(d1(k),d2(k) . . . dN(k))T, dn(k)εC, k=1 . . . K, n=1 . . . N, K,N ε IN,
- each of the data vectors being composed of N complex data symbols dn(k) to the base m with a data symbol period length Ts;
- K subscriber stations for transmitting the data blocks with application of a spread code, assigned to a respective subscriber station k, k=1 . . . K, with Q subcarriers distributed uniformly within an RF radio frequency band;
- a reception site using said spread code and a CDMA detector device for decoding the data blocks;
- a number of data symbols dn(k) transmitted simultaneously by a specific subscriber station k being one and all the data symbols dn(k) of a subscriber station being transmitted successively;
- said transmission using the Q subcarriers of bandwidth Bs=BU/Q=1/Ts, the subcarriers numbered with g=1 . . . Q each having a single center of frequency fq, q=1 . . . Q, in accordance with f q = q - 1 T s , q = 1 … Q
- each data symbol dn(k) of a subscriber station being spread over all the Q subcarriers of the bandwidth Bs by a subscriber-specific signature code sequence
- c(k)=(c1(k), c2(k) . . . cQ(k))T, cq(k)εC, k=1 . . . K, q=1 . . . Q, K, QεIN
- composed of chips cq(k), each chip being assigned to a particular subcarrier;
- a linearly modulated signal, which is transmitted by a subscriber station, k, k=1 . . . K which is given in the equivalent low-pass filter region by d _ ( k ) ( t ) = ∑ n = 1 N d _ n ( k ) · c _ ( k ) ( t - [ n - 1 ] T s ;
- c _ ( k ) ) ,
- linear MC-CDMA spread modulation being formed by samplings of a c(k) (t;c(k)) made at a rate 1/Tc, the sampled values ζq(k), q=1 . . . Q, K produced by these samplings giving rise to vectors
- ζ(k)=(ζ1(k), ζ2(k) . . . ζQ(k))T, ζq(k)εC, k=1 . . . K, q=1 . . . Q, K, QεIN;
- a relation between the vectors ζ(k) and the spread code vectors c(k) being given the equation ζ(k)=Dc(k) with a matrix D _ = ( D _ α , β ) , D _ α , β = 1 Q exp { j 2 π Q ( α - 1 ) ( β - 1 ) } , α , β = 1 … Q
- of an inverse discrete Fourier transformation (IDFT), a vector matrix ζ(k) containing Q column vectors δ _ ( q ) = ( δ _ 1 ( q ) , δ _ 2 ( q ) … δ _ Q ( q ) ) T , δ _ α ( q ) = 1 Q exp { j 2 π Q ( α - 1 ) ( q - 1 ) } ,
- α=1 . . . Q, so that D=(δ(1), δ(2) . . . δ(Q))
- and thus
- ζ(k)=(c1(k)δ(1)+c2(k)δ(2)+ . . . +cQ(k)δ(Q))
- is obtained;
- since each chip cq(k) is assigned to a particular subcarrier q, the equation ζ(k)=Dc(k) is interpreted such that columns δ(q), q=1 . . . Q of the matrix D represent the Q subcarriers and rows of the matrix D represent Q time moments within the data symbol period length Ts during which sampled values are taken;
- and
- a result of the equation ζ(k)=Dc(k) being a vector ζ(k) with elements ζg(k) which result from a linear combination of the chips cq(k).
Dependencies are inferred from the claim text.