This page on WiMAX terminology describes terms related to fixed wimax(16d/OFDM) and mobile wimax(16e/OFDMA) standards. It include OFDM, frame, burst, symbol, sampling factor, physical slot, TTG, RTG, OFDMA, SOFDMA, symbol, slot, burst, symbol, slot, DLMAP, ULMAP, UCD, DCD, UIUC, DIUC, Uplink, Downlink, point-to-point, point to multipoint, CID, SFID and more.
Fixed WiMAX(16d) Terms
OFDM: Orthogonal frequency division multiplexing, used in physical layer of downlink and Uplink of Fixed WiMAX.
Frame: Fixed WiMAX defines 2 types of frames, TDD and FDD. TDD frame is adopted by WiMAX Forum. Frame duration is 5ms and 10ms. Based on bandwidth either 3.5MHz or 7MHz numbers of symbols vary in each frame.
Refer our page on WiMAX Frame Structure for more information on fixed wimax(OFDM) and Mobile wimax(OFDMA) frame structure in detail.
Burst: Burst concept is used here, which is composed one or more OFDM symbols and will carry MAC PDUs.
Symbol: OFDM symbol composed of total 256 carriers, here 192 are data subcarrier, 8 are pilot subcarrier, 1 is DC carrier and rest are used as guard subcarriers.
Sampling Factor: This parameter, in conjunction with BW and Nused determines the subcarrier spacing, and the useful symbol time.
As per standard there are two values of n i.e. either 8/7 or 28/25 based on channel bandwidth selected.
Sampling Frequency, Fs= (n* BW/8000)*8000
Physical slot: It is the minimum unit of BW allocation used by Base station in giving resources to the SSs.
PS duration =4/Fs
TTG: Transmit to receive turnaround time.Gap between downlink subframe end and start of uplink subframe in TDD frame.
This helps BS to switch from Tx to Rx mode. During this period BS will not transmit any data.
This is not applicable for FDD frame.
RTG: Receive to transmit turnaround time.
Mobile WiMAX(16e) Terms
OFDMA: Orthogonal Frequency Division Multiple Access, used in physical layer of Mobile WiMAX in both the downlink and uplink.
Refer our page on OFDM_versus_OFDMA which covers difference between OFDM and OFDMA concepts.
SOFDMA: Scalable OFDMA. Here Subcarrier spacing remains same as FFT and BW varies in proportion to each other.
Frame: Frame is made up of time-frequency grid. On time axis it is OFDM symbols and on frequency axis it is sub channels. One sub channel is composed of more than one subcarriers which are permuted and assigned to sub channels.
Symbol: Consists of more than one subcarriers based on FFT size. There are 512 and 1024 FFTs supported by major equipment manufacturers of mobile WiMAX around the world and is also finalized by WiMAX forum.
Slot: The slot is the minimum resource allocated by Base station to Mobile subscribers in Mobile WiMAX. It is basically composed of sub channel along with OFDMA symbols. 2-dimentional resource allocation is used here. For downlink PUSC it is 1 sub channel across 2 OFDMA symbols and for uplink PUSC it is 1 sub channel across 3 OFDMA symbols. For Downlink FUSC it is 1 sub channel across 1 OFDMA symbol. In AMC zone it 2 sub channel versus 3 OFDMA symbols.
DLMAP: Downlink MAP, basically carry location information of downlink bursts in the TDD frame.
This is mentioned in units of symbols w. r. t. start of the frame,
ULMAP: Uplink MAP, basically carry location information of uplink sub frame in the TDD frame.
UCD: Uplink Channel descriptor, defines modulation-code rate of the uplink burst in accordance
with the UIUC mapping, READ MORE.
DCD: Downlink Channel descriptor, defines modulation-code rate of the downlink burst in
accordance with the DIUC mapping.
UIUC: Uplink Interval Usage Code
DIUC: Downlink Interval Usage Code
Uplink: Transmission from Subscriber Stations (SSs) to Base Station (BS)
Downlink: Transmission from BS to SSs.
Point-to-point:Topology where one SS can talk to another SS directly as used in mesh topology.
Point-to-multi-point: Topology where one SS can talk to another SS through BS.
CID: Connection Identifier, a 16 bit value that identifies a
connection to equivalent peers in the MAC of the Base station (BS)
and Subscriber Station (SS). It maps to a service flow identifier (SFID-32 bit)
which defines the QoS parameters of the service flow associated with that connection,
SFID: A 32 bit quantity that uniquely identifies a service flow to both the
subscriber station and base station.
Other useful Terminologies
Links to WiMAX MAC Layer resources
REG REQ and REG RSP
SBC REQ and SBC RSP
DSA REQ and DSA RSP
DLMAP and ULMAP
WiMAX Ranging Procedure
WiMAX Bandwidth Request procedure
WiMAX Network Entry Procedure
WiMAX CID vs SFID
WiMAX FCH header format
WiMAX TLV Format basics
WiMAX Network Interface types
WiMAX QoS Classes