Contents
- 1 What are the properties of orthogonal codes?
- 2 Which uses orthogonal codes?
- 3 What do you mean by orthogonal codes?
- 4 Why is near far a problem in CDMA?
- 5 What is an orthogonal cover code?
- 6 How do I generate a Walsh code?
- 7 How often do orthogonal codes have to be rotated?
- 8 Why is a vector code an orthogonal code?
What are the properties of orthogonal codes?
Truly orthogonal codes: Two codes are said to be orthogonal if when they are multiplied together the result is added over a period of time they sum to zero. For example a codes 1 -1 -1 1 and 1 -1 1 -1 when multiplied together give 1 1 -1 -1 which gives the sum zero.
Which uses orthogonal codes?
Which uses orthogonal codes? Explanation: Synchronous CDMA uses orthogonal codes and asynchronous CDMA uses pseudorandom codes.
How do you generate orthogonal codes?
The simplest way to get an orthogonal code dictionary is to generate a Hadamard/Walsh matrix. All the rows and columns of this matrix are mutually orthogonal. You can use a couple of its rows or columns as your codes.
What do you mean by orthogonal codes?
CDMA (Code Division Multiple Access) is a communication technique that allows multiple users to communicate simultaneously over one frequency. This is achieved through the use of spreading codes, whereby a single data bit is “spread” over a longer sequence of transmitted bits. Such codes are known as orthogonal codes.
Why is near far a problem in CDMA?
CDMA near far problem basics The CDMA near far problem arises because handsets may be anywhere within the particular cell boundaries. Some handsets will be close to the base station, whereas others will be much further away.
What is orthogonal coding?
In computer programming, orthogonality means that operations change just one thing without affecting others. The term is most-frequently used regarding assembly instruction sets, as orthogonal instruction set.
What is an orthogonal cover code?
Orthogonal cover codes are length-2 Walsh codes extended over the two DM RS in the subframe as shown in Figure 7.4. OCCs provide two benefits: they improve the reliability in separating the different RS from each other, especially when SU-MIMO or MU-MIMO transmission contains several transmission layers.
How do I generate a Walsh code?
To Generate Walsh Codes used in IS-95 (which utilizes 64 Walsh codes of size 64 bits each, use : [H]=generateHadamardMatrix(64). This will generate 64 Walsh Codes of length 64-bits (for each code).
Which is a feature of a PN code?
A feature of PN codes is that if the same versions of the PN code are time shifted, then they become almost orthogonal, and can be used as virtually orthogonal codes within a CDMA system. Truly orthogonal codes: Two codes are said to be orthogonal if when they are multiplied together the result is added over a period of time they sum to zero.
How often do orthogonal codes have to be rotated?
However, for every transmission combination, each code must be rotated in all possibilities relative to each other. So for 4-user, 8-bit codes, this program will take 8 4 =4096 times as long as the previous program. However, the run time is still acceptable.
Why is a vector code an orthogonal code?
In a more practical sense, vectors are orthogonal if they allow correct decoding of transmitted data. This definition may sound contrived at first, and slower to calculate, but its usefulness will become apparent later as we investigate chip synchronization issues.
Why are the CDMA spreading codes orthogonal to each other?
Being orthogonal, the different CDMA signals are able to operative with little mutual interference. The CDMA spreading codes are used to increase the bandwidth of the signal to gain the benefits of spread spectrum communications, but reducing the mutual interference requires the codes are orthogonal.