Channel Access

Channel Access
Notes

It is also called Multiple Access.

Multiple access schemes are based on multiplexing.

Channel Based Methods

Code Division Multiple Access (CDMA) / Spread Spectrum Multiple Access (SSMA)
- Direct Sequence Code Division Multiple Access (DS-CDMA)
- Frequency Hopping Code Division Multiple Access (FH-CDMA)
- Multi Carrier Code Division Multiple Access (MC-CDMA)
- Wideband Code Division Multiple Access (W-CDMA)
- Time Division Code Division Multiple Access (TD-CDMA)
- Time Division Synchronous Code Division Multiple Access (TD-SCDMA)
Frequency Division Multiple Access (FDMA)
- Frequency Division Multiplexing (FDM) based:
  - Orthogonal Frequency Division Multiple Access (OFDMA)
  - Single Carrier Frequency Division Multiple Access (SC-FDMA) / Linearly Pre-coded OFDMA (LP-OFDMA)
- Wavelength Division Multiplexing (WDM) based:
  - Wavelength Division Multiple Access (WDMA)
Time Division Multiple Access (TDMA)
- Multi Frequency Time Division Multiple Access (MF-TDMA)
- Self-organized Time Division Multiple Access (STDMA)
- Statistical Time Division Multiplexing Multiple Access (STDM-MA) / Packet Mode
- Dynamic Time Division Multiple Access (Dynamic TDMA)
Space Division Multiple Access (SDMA)
- High Capacity Spatial Division Multiple Access (HC-SDMA)

Packet Mode Methods

General (Statistical Time Division Multiple Access Methods)

Carrier Sense Multiple Access (CSMA)
Carrier Sense Multiple Access with Collision Detection (CSMA/CD)
Carrier Sense Multiple Access with Collision Avoidance and Resolution using Priorities (CSMA/CARP)
Multiple Access with Collision Avoidance (MACA)
Multiple Access with Collision Avoidance for Wireless (MACAW)
Bitwise Arbitration based on constructive interference as used on CAN bus
Token bus
Token Ring
Token passing
Dynamic Time Division Multiple Access (Dynamic TDMA)

Wireless

Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA)
ALOHA and slotted ALOHA
Reservation ALOHA (R-ALOHA)
Mobile Slotted Aloha (MS-ALOHA)
Code Division Multiple Access (CDMA)
Orthogonal Frequency Division Multiple Access (OFDMA)
Orthogonal Frequency Division Multiplexing (OFDM)

Duplexing Methods

Full Duplexing

Time Division Duplexing (TDD)
Frequency Division Duplexing (FDD)
Echo Cancellation

Notes

Channel Based Methods

Code Division Multiple Access

Direct Sequence Code Division Multiple Acces

DS-CDMA (Direct Sequence Code Division Multiple Access) is a multiple access scheme based on DSSS, by spreading the signals from/to different users with different codes.

It is the most widely used type of CDMA.

Frequency Hopping Code Division Multiple Access

FH-CDMA (Frequency Hopping Code Division Multiple Access) is a multiple access scheme based on FHSS.

As an example, the Bluetooth communication system is based on a combination of Frequency Hopping and either CSMA/CA Statistical Time Division Multiplexing communication (for data communication applications) or TDMA (for audio transmission).

All nodes belonging to the same user (to the same piconet) use the same frequency hopping sequence synchronously, meaning that they send on the same frequency channel, but CDMA/CA or TDMA is used to avoid collisions within the VPAN (Virtual Personal Area Network).

Frequency-hopping is used by Bluetooth to reduce the cross-talk and collision probability between nodes in different VPANs.

Multi Carrier Code Division Multiple Access

Wideband Code Division Multiple Access

Time Division Code Division Multiple Access

Time Division Synchronous Code Division Multiple Access

Frequency Division Multiple Access

FDMA (Frequency Division Multiple Access) methods are based on Frequency Division Multiplexing (FDM).

A related method is Wavelength Division Multiple Access (WDMA), which is based on Wavelength Division Multiplexing (WDM).

Based on Frequency Division Multiplexing

Orthogonal Frequency Division Multiple Access

Single Carrier Frequency Division Multiple Access

Single Carrier FDMA (SC-FDMA) is also known as Linearly Precoded OFDMA (LP-OFDMA).

It is based on Single Carrier Frequency Domain Equalization (SC-FDE).

Based on Wavelength Division Multiplexing

Wavelength Division Multiple Access

Time Division Multiple Access

It is based on Time Division Multiplexing (TDM).

Multi Frequency Time Division Multiple Access

It combines TDMA and FDMA, like in GSM.

In GSM, the frequency channel is divided into eight time slots, of which seven are used for seven phone calls, and one for signaling data.

Self-organized Time Division Multiple Access

Statistical Time Division Multiplexing Multiple Access

Statistical multiplexing is facilitated through packet mode communications.

Hence this covered under Packet Mode methods.

Dynamic Time Division Multiple Access (Dynamic TDMA)

Space Division Multiple Access

Use directional antennas and power modulation to refine spatial transmission patterns.

High Capacity Spatial Division Multiple Access

Power Division Multiple Access (PDMA)

Power-division multiple access (PDMA) scheme is based on using variable transmission power between users in order to share the available power on the channel.

Packet mode methods

Packet mode channel access methods select a single network transmitter for the duration of a packet transmission. Some methods are more suited to wired communication while others are more suited to wireless.

It generally means Statistical Time Division Multiplexing methods. Packet mode communications are also facilitated by CDMA and Random Frequency Hopping OFDMA (RFH-OFDMA).

Common Statistical Time Division Multiplexing Multiple Access protocols for wired multi-drop networks include:

Carrier-Sense Multiple Access with Collision Detection (CSMA/CD) (Used in Ethernet and IEEE 802.3)
Multiple Access with Collision Avoidance (MACA)
Multiple Access with Collision Avoidance for Wireless (MACAW)
Carrier-Sense Multiple Access (CSMA)
Carrier-Sense Multiple Access with Collision Avoidance and Resolution using Priorities (CSMA/CARP)
Bitwise Arbitration based on constructive interference as used on CAN bus
Token bus (IEEE 802.4)
Token Ring (IEEE 802.5)
Token passing (used in FDDI)
Dynamic Time Division Multiple Access (Dynamic TDMA)

Common multiple access protocols that may be used in packet radio wireless networks include:

Carrier-sense multiple access with collision avoidance (CSMA/CA) (used in IEEE 802.11/WiFi, potentially using a distributed coordination function)
ALOHA and slotted ALOHA (used in ALOHAnet)
Reservation ALOHA (R-ALOHA)
Mobile Slotted Aloha (MS-ALOHA)
Code Division Multiple Access (CDMA)
Orthogonal Frequency Division Multiple Access (OFDMA)
Orthogonal Frequency Division Multiplexing (OFDM)

Organized by Collision Handling

Collision recovery

ALOHA, Slotted ALOHA, R-ALOHA, AX.25, CSMA/CD

Collision avoidance

MACA, MACAW, CSMA, CSMA/CA, DCF, PCF, HCF, CSMA/CARP

Collision-free

Token Ring, Token bus, MS-ALOHA

Duplexing methods

Where these methods are used for dividing forward and reverse communication channels, they are known as duplexing methods.

Some types of full-duplexing methods are:

Time Division Duplexing (TDD)
Frequency Division Duplexing (FDD)
Echo Cancellation