3.6.1 Proofs for Section 3.3.1Proof of Theorem 3.1Denote and . We have the following differential (at Y ): Equation 3.231
The differential of the form II group -blind detector, Equation 3.232
is then given by Equation 3.233
It then follows from Lemma 2.6 that is asymptotically Gaussian. To find C w , notice that u 1 range ( U s ). Hence, by Proposition 2.6, we have Equation 3.234
with Equation 3.235
Equation 3.236
Therefore, the asymptotic covariance of is given by Equation 3.237
It is easily verified that QY u 1 = . Using this and the facts that w 1 = Y u 1 and QU n = U n , by substituting (3.234) into (3.237), we obtain (3.61). Proof of Corollary 3.1In this appendix e k denotes the k th unit vector in and denotes the k th unit vector in . Denote and . Denote further that and . Note that ( Ys k ) is the linear MMSE detector for the k th user , given by Equation 3.238
Denote Equation 3.239
Equation 3.240
Equation 3.241
Equation 3.242
First we compute the term tr ( C w C r ). Using (3.61) and the facts that , we have Equation 3.243
The term ( ) in (3.243) can be computed as Equation 3.244
Using the fact that , the term tr ( QYQ T X ) in (3.243) is given by Equation 3.245
To compute the second term in (3.243), first note that . We have Equation 3.246
where the first equality follows from the fact that QY = . Moreover, Equation 3.247
where we used the fact that YXY = Y . In (3.246) is given by Equation 3.248
Equation 3.249
Substituting (3.247) and (3.249) into (3.246) we obtain the second term in (3.243): Equation 3.250
Finally, we compute t in the last term in (3.243). By definition, Equation 3.251
where Equation 3.252
Equation 3.253
Equation 3.254
with . Substituting (3.244), (3.245), (3.250), and (3.251) into (3.243), we have Equation 3.255
Moreover, we have Equation 3.256
Next we compute w 1 2 . Since Equation 3.257
Equation 3.258
we have Equation 3.259
By (3.255) “(3.259) we obtain the corollary. SINR Calculation for Example 2Substituting (2.338) “(2.340) and A 2 = A 2 I K into (3.66) “(3.68), we have Equation 3.260
Equation 3.261
Equation 3.262
Equation 3.263
Equation 3.264
where , , denotes an all-1 -vector, and denotes an all-1 ( )-vector. After some manipulations, we obtain the following expressions: Equation 3.265
Equation 3.266
Equation 3.267
Equation 3.268
Equation 3.269
Equation 3.270
Substituting (3.265) “(3.270) into (3.69) “(3.72), and letting Equation 3.271
Equation 3.272
Equation 3.273
Equation 3.274
Equation 3.275
we obtain (3.82). 3.6.2 Proofs for Section 3.3.2Proof of Theorem 3.2We prove this theorem for the case of a linear group-blind hybrid detector (i.e., ). The proof for a linear group-blind MMSE detector is essentially the same. Denote e k as the k th unit vector in . Let Q 1 be an orthogonal transformation such that Equation 3.276
For any , denote . The corresponding projection matrix in the Q 1 - rotated coordinate system is Equation 3.277
Equation 3.278
Equation 3.279
Denote Equation 3.280
Equation 3.281
where the dimension of is (N “ ) x (N “ ). Hence Equation 3.282
Let the eigendecomposition of be [1]
Equation 3.283
Define another orthogonal transformation, Equation 3.284
For any , denote . In what follows, we compute the asymptotic covariance matrix of the detector in the Q 1 Q 2 -rotated coordinate system. In this new coordinate system, we have Equation 3.285
Equation 3.286
Equation 3.287
Equation 3.288
Furthermore, after rotation, has the form Equation 3.289
for some . After some manipulations, the form I group-blind hybrid detector in the new coordinate system has the form Equation 3.290
where E s consists of the first columns of (i.e., = [ E s E n ]). Let the estimated autocorrelation matrix in the rotated coordinate system be Equation 3.291
Let the corresponding eigendecomposition of be Equation 3.292
Then the estimated detector in the same coordinate system is given by
Note that in such a rotated coordinate system, estimation error occurs only in the first elements of . Denote Equation 3.293
Equation 3.294
Hence is a function of and its differential at (i.e., and is given by Equation 3.295
By Lemma 2.6, is then asymptotically Gaussian with a covariance matrix given by Equation 3.296
We next compute the three terms T 1 , T 2 , and T 3 in (3.296). We first compute T 1 . Denote z k and x k as the subvectors of containing, respectively, the first N “ and the last elements of (i.e., ) for k = + 1, . . . , K . Let . It is clear that range ( U s ), and therefore range ( ). Expressed in the rotated coordinate system, we have range ( E s ). We can therefore apply Proposition 2.6 to T 1 to obtain Equation 3.297
with Equation 3.298
Equation 3.299
The term T 2 can be computed following a similar derivation as in the proof of Theorem 1 for the DMI blind detector. Specifically, we have, similar to (2.302), Equation 3.300
Writing (3.300) in matrix form, we have Equation 3.301
with Equation 3.302
Hence the second term in (3.296) is Equation 3.303
where we have used the fact that , and the definition in (3.293). Finally, we calculate T 3 . Denote . By following the same derivation leading to (2.313), we get for i K “ , Equation 3.304
As before, we only have to consider [ T 3 ] i,j for i,j K “ or i,j > K “ . However, all terms corresponding to i,j > K “ will be nulled out because of the multiplication of Y on T 3 . Using Lemma 2.5, we then get (for i,j K “ ) Equation 3.305
Writing this in matrix form, we have Equation 3.306
Equation 3.307
Hence the third term in (3.296) is given by Equation 3.308
Substituting (3.297), (3.303), and (3.308) into (3.296), we obtain Equation 3.309
where D 1 and D 2 are given, respectively, by (3.299) and (3.302), and t is given by (3.298). Theorem 3 is now easily obtained by transforming (3.309) back to the original coordinate system according to the following mappings: , , , and . |