NETWORK PERFORMANCE IMPROVEMENT USING AN ANTENNA ARRAY

Denso QR Bar Code recognizer in .netUsing Barcode Control SDK for .net framework Control to generate, create, read, scan barcode image in .net framework applications.

Desired cell

Qr Codes barcode library on .netgenerate, create qr code none for .net projects

Interfering cell

scanning quick response code on .netUsing Barcode reader for Visual Studio .NET Control to read, scan read, scan image in Visual Studio .NET applications.

BS dus

Barcode barcode library for .netgenerate, create bar code none in .net projects

dl D

Visual Studio .NET bar code readeron .netUsing Barcode recognizer for .net framework Control to read, scan read, scan image in .net framework applications.

FIGURE 9.31. Co-channel interference between a desired and an interfering cell.

Co-channel interference will occur when the ratio of the received (e.g., wanted) signal envelope, S, to the interfering signal envelope, I, is less than some protection ratio pr (a threshold), that is [168], S I pr 9:48

Web Pages qr codes implementationon .netuse an asp.net form quick response code creation toreceive qr-codes for .net

Now we consider only one co-channel cell as an i part of a cellular network, as shown in Figure 9.31. Assume that only propagation-loss effects are proportional to distances dMS and dI between the desired mobile subscriber and each of the desired and interfering BS, respectively. Then, S dg gI I dMS pr 9:49

QR Code JIS X 0510 generating on visual basic.netusing barcode integrating for .net framework control to generate, create qr code 2d barcode image in .net framework applications.

where g is the loss exponent. So, for a given protection we get [168 169] dI dMS pr 1=g 9:50

DataMatrix creator for .netusing barcode encoding for visual studio .net crystal control to generate, create data matrix image in visual studio .net crystal applications.

In the case when the desired user lies along a straight line between two base stations (the worst case for a user), the co-channel reuse ratio is Q D=Rcell 1 dI =dMS 1 p1=g r 9:51

UCC.EAN - 128 encoding with .netuse vs .net ucc - 12 writer togenerate gs1-128 with .net

For a given protection ratio and modulation scheme, this expression de nes the minimum spacing between co-channel cells in order to avoid interference. For six co-channel cells interferers (Fig. 9.32), which lie only in the rst tier of co-channel cells, we have instead of (9.49), the following expression [103]: S d g MS g I 6dI pr 9:52

Barcode development on .netuse visual .net barcode generator togenerate bar code on .net

ADAPTIVE ANTENNAS FOR WIRELESS NETWORKS

.net Framework international standard serial number integrationin .netuse visual .net issn maker toincoporate international standard serial number on .net

nd tie

Fir st

Barcode development in excelgenerate, create barcode none for microsoft excel projects

tier

Display barcode with word documentsusing barcode creation for office word control to generate, create barcode image in office word applications.

Seco

Control qr data in .net c#to produce qr code jis x 0510 and qr code data, size, image with c#.net barcode sdk

BS Desired cell

Make code 39 full ascii in vb.netgenerate, create uss code 39 none with visual basic.net projects

Interfering cells

Print matrix barcode on word documentsusing barcode implement for microsoft word control to generate, create 2d matrix barcode image in microsoft word applications.

FIGURE 9.32. Scheme of how to eliminate the co-channel interference between neighboring cells operating at the same frequency band.

barcode library with noneUsing Barcode Control SDK for None Control to generate, create, read, scan barcode image in None applications.

The co-channel reuse factor can be expressed as [167] Q D=Rcell 6 S=I 1=g 9:53

Control code128b data in vb.net barcode code 128 data for visual basic

To see how these parameters in uence the co-channel interference occurrence, let us de ne some other parameters of the network. First, we assume that all users are uniformly distributed per cell with a blocking probability of service Pbl constant for all cells. Blocking probability is measured, by the number of users/calls that cannot be served during the period of service. The parameter A (in Erlangs) de nes the traf c intensity offered, where Erlang is a measure of traf c intensity de ning the quantity of traf c on a channel or group of channels (users) per unit time. Then the actual traf c carried is equal to A(1 Pbl ) Erlangs, and the so-called outgoing channel usage ef ciency or loading factor becomes [169] Z A 1 Pbl =nc 9:54

where nc is the total number of channels allocated per cell. We now assume that instead of an omnidirectional base-station antenna we have an adaptive one, which generates M ideal beams with a bandwidth of 2p=M, and a gain equal to that of omniantenna. Each adaptive beam will only carry the channels that are assigned to the mobiles within its coverage area. So, any mobile or group of mobiles can be tracked by using adaptive base-station antennas, as sketched in Figure 9.26.

NETWORK PERFORMANCE IMPROVEMENT USING AN ANTENNA ARRAY

As the occurrence of co-channel interference between subscribers is a statistical problem, instead of the probability of co-channel interference, Z, we use the outage probability, P S I pr . This probability determines the frequency of failing to obtain satisfactory reception at the mobile in the presence of interference. For identical cells, having equal probability of call blocking, there will be in average nc Z active channels in each cell. Then, for the omnidirectional base-station antenna, assuming the desired mobile is already allocated a channel, the probability of that channel being active in an interfering cell is the required outage probability, given by P S I pr number of active channels Znc Z nc total number of channels 9:55

Hence, when the desired mobile is in the region of co-channel interference for the omniterminal antennas, the outage probability is identical to the probability of cochannel interference. For adaptive antennas with M beams per base-station, we have nc Z=M channels per beam with a uniform distribution of subscribers. Here, a desired mobile is always covered by at least one beam from the co-channel cell. Then, the outage probability is equal to the probability that one of the channels in the aligned beam is the corresponding active co-channel (i.e., the channel that has been allocated to the desired mobile). Thus, this probability equals P S I pr number of channels per beam Znc =M Z total number of channels nc M 9:56

Thus, the co-channel interference decreases with an increase in the number of antenna elements in the adaptive array or the number of beams in the multibeam antenna. Now using a simple geometry presented in Figure 9.31, it can be shown, that for the six co-channel cells in the rst tier, the outage probability at the regions of interference equals P S I pr Z 6 M 9:57

that is, it decreases M 6 times with an increase of M. This means that there are six beams aligned onto the desired mobile at any time, and the outage probability within the region of interference is de ned by the probability that the active co-channel is in each of these beams. For more details the reader is referred to References [103,170 172]. It is the spatial ltering capabilities of adaptive antennas that reduce cochannel interference. In general, an adaptive array requires some information about the desired signal, such as the direction of its source, a reference signal, or a signal that is correlated with the desired signal. In situations where the precise direction of the signal is