Radio Interface Flashcards
What is FDD?
FDD, or Frequency Division Duplex, describes a pair of frequencies.
Typically used in areas with available spectrum
What is TDD?
TDD, Time Division Duplex, handset and tower share the same frequency.
Typically used areas with limited spectrum space.
What is a UARFCN?
UTRA Absolute Radio Frequency Channel Number
Commonly referred to as a “Channel.”
UARFCN represents only a single frequency, this means that in FDD systems, the UE and Node B have their own UARFCNs.
In a TDD system, only one UARFCN is used.
What is CDMA?
Code Division Multiple Access
Users and are the same frequency but are assigned a code
Limited by the number codes available
What are the characteristics of a UMTS channel?
3.84mHz Wide
5Mhz between WCDMA signals
Spread with a chipping rate of 3.84Mcps
What is DSSS?
Direct Sequence Spread Spectrum
Takes a narrowband signal and “spreads” the data across a wider spectrum
What is the difference between a bit and a chip?
Bit or binary digit: is either a 1 or a 0 that is used to convey data in digital systems
Chip: a pulse of information in DSSS code. Used to spread a transmitted signal. Multiple chips represent a bit symbol
What is the chipping rate?
3.84Mcps
What are scrambling codes?
Pseudorandom Noise codes just like the long and short codes used in CDMA
What are synchronization codes?
Synchronization Codes are broadcast in the clear (not scrambled) on the Synch Channel.
Used to help UEs more efficiently identify the PSC being used on a cell.
There are 64 combinations of Sync Codes, correlated to the 64 Code groups
What are orthogonal variable spreading factor codes?
OVSF Codes are the codes used when spreading a signal.
Same exact code matrix used for Walsh Codes in CDMA2000.
512 Available on the downlink, 256 available on the uplink.
Higher spreading rates result in greater users, but slower data rates, and vice versa
