16 terms

CDMA, WCDMA

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Channel Division Multiple Access (CDMA)
Used exclusively in 3G and offers a less definitive limit on capacity in comparison to TDMA. Enables adjacent cells to operate on the same frequency band.
Superposition
The synchronization of two streams of data sent simultaneously in CDMA. It gives a result which is a mathematical addition of the two states (e.g. such as 1 + 1) and it is ordinary addition, not binary.
Orthogonality
When two different data streams sent simultaneously, creates separate channels of communication. The streams don't interact which stops any interference and can be recovered independently.
Bipolar
When a '0' in binary form becomes a '-1' and a '1' in binary form becomes a '+1'.
Correlation
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Processing gain
When the 'bits' are replaced with 'chips', the frequency spectrum is spread over a wider band of frequencies, giving enhanced immunity to certain types of noise. It is related to the number of chips used per bit.
Spreading Factor
When the degree of spectrum spreading can be quantified. It is equal to the number of chips used to represent a single bit of data in the coding process. If 4 chip codes are used it has a s... f... of 4. Calculated with formula: 'chip rate / data rate'.
Wideband Code Division Multiple Access (WCDMA)
Used in 3G, it can carry data at higher speeds
UMTS
Universal Mobile Telecommunications System
Scrambling Codes
Used to create orthogonal streams of data. Can uniquely identify the sources of signals in either direction (downlink or uplink) through the different scrambling codes allocated to UE.
Pseudo Noise Codes
Also known as 'Scrambling Codes' or 'Pseudo Random Codes' because they have a random character within them that makes them look like noise. The noise-like character is essential to their function.
Near Far problem
When signals from near-by equipment swamp those from equipment further away. The base station combats this by sending signals to the UE to regulate the signal to the desired power levels.
Orthogonal Frequency Division Multiple Access (OFDMA)
Involves simultaneous use of many wireless carrier signals (subcarriers). Separate subcarriers can be allocated to different streams of data and different users. Bandwidth can be allocated dynamically because the number of subcarriers can change dynamically.
Carrier wave
A radio wave which has been modulated to carry data.
Convolutional Turbo Code
Type of code using convolutional methods which are separated by interleavers.
Block Turbo Code
Type of code concatenated into blocks such as Hamming code.