MAC Architecture Components

The main components the Magic WAND MAC layer are (see Figure 2):

• The Inter-Control Communication (ICC), which allows the MASCARA FE’s to interface, for control purposes, with the upper layers. It thus allows cross-layer communications to exchange information between the MASCARA layer and the entities located within upper layers such as at the Q.2931m level for the MT, or the MRR for the AP. Furthermore, this FE is functionally identical in the AP and in the MT.

• The MASCARA Control FE which is responsible for the ”non stationary”, control functions of the MASCARA protocol, related or not to the control of the radio modem. For instance this FE is in charge of the association and re-association procedures. It is also involved in the hand-over procedure by receiving (through ICC) some requests coming from upper layer components. This FE differs between the AP (master side) and the MT (slave side). Moreover, this functional entity might contain functions of the Radio Resource Management, such as Wireless Connection Admission Control [ZAND97]. Finally, functions to control the channel and means to share it when interference occurs (use of Dynamic Channel Allocation among different APs) are also part of MASCARA Control.

CEC Deliverable No: AC085/INT/ACT/DS/P/035/b1

Title of Deliverable: Wireless ATM MAC – Final Report

• The Control Segmenting Reassembly FE segments the control messages received from Mascara_Control into cells, and reassembles cells received into a control message delivered to Mascara_Control. This FE is functionally identical in the AP and in the MT.

• The W-DLC, which is split into the transmit part (W-DLC Xmit) and the receive part (W-DLC Rcv). This FE is responsible for recovering (even partly) from the bad quality of the transmission channel thanks to techniques like ARQ, ACK or CRC. The first part is in charge of building the cell train which will later be sent over the air as a MPDU payload, whereas the second part is in charge of sending to the MAC-ATM interface the cells which were previously received within MPDU payloads. Furthermore, this FE is functionally identical in the AP or in the MT.

• The MAC Data Pump manages the slot map according to the connection profile (AAL) and the Quality of Service (QoS) parameters, and sends and receives MPDU to/from the physical layer. This FE contains:

 the MASCARA scheduler and differs thus between the AP (master side) and the MT (slave side).Scheduler [DRMP96]

 Frame Processor; the interface to the physical layer, performs MPDU error control and ATM cell CRC calculations.

 MPDU transmit and receive modules

A T M L a y e r

M A S C A R A L A Y E R

L a y e r C o n t r o l P r o to c o l

M e s s a g e E n c a p s u la ti o n U n it

M A S C A R A C o n tr o L

C o n tr o l S e g m e n ta t io n

& R e a s s e m b ly

W ir e le s s D a ta L in k C o n tr o l

M A S C A R A D a ta P u m p

P h y s ic a l L a y e r

Figure 2 MASCARA Functional Entities

These components communicate with each other to exchange useful information for the DLC operation. Moreover, some DLC components will communicate with some higher layer functions to acquire critical information or to inform them about some incidents (e.g. handover).

CEC Deliverable No: AC085/INT/ACT/DS/P/035/b1

Title of Deliverable: Wireless ATM MAC – Final Report

The previous MASCARA FE’s exchange signals with the external world thanks to the two following interfaces:

• The MAC-ATM interface, through which the MASCARA FE’s interact with the ATM layers for the reception or transmission of ATM cells. Such ATM cells may either carry ATM bearer services traffic or control traffic (such as some control information exchanged during hand-over procedure). Thus this interface belongs both to the data plane and the control plane. Furthermore, this interface is functionally identical in the AP or in the MT.

• The MAC-PHY interface, through which the MASCARA FE’s interact with the radio transceiver, either for the transfer (in/out) of MPDU, or for the exchange of control information (such as channel selection, RSSI, transmit power setting or dormant state setting). This interface can thus be seen as belonging both to the data and control planes. Furthermore, this interface is almost identical in the AP or in the MT, as it only differs in the way the time slot clock is handled.

A more detailed description of the MAC components, as well as of the inter-component communication will be given in the following sections.

The MAC components proposed can be matched with the common reference model that the ATM Forum and ETSI BRAN use for wireless ATM (see Figure 3). Some of the MAC Control functions are in the PAC and TAC entities (Access Control entities at the MT and the AP respectively). The W-DLC functionality can be included in the ATM Connection function (ATMC). The RRM and Scheduling functions are implemented within the Radio Resource Control (RRC) function. The Cell Handling functions are mapped to the Radio Transmission and Reception functions (RTR).

PATMC

: logical interface : physical interface

Wireless AP Mobility Enabled Switch Inf.7

Inf. 5

External ATM network

Figure 3 ATM Forum WATM – BRAN common reference model

APCF (AP Control Function) ATMC (ATM Connection function)

CCF (Call control and Connection control Function) MMF (Mobility Management Function)

PAC (Portable terminal Access Control function) PATMC (Portable ATM Connection function)

CEC Deliverable No: AC085/INT/ACT/DS/P/035/b1

Title of Deliverable: Wireless ATM MAC – Final Report

PCC (Portable Call control and Connection control function) PMM (Portable Mobility Management function)

PRRC (Portable Radio Resource Control function) PRTR (Portable Radio Transmission and Reception) RRC (Radio Resource Control function)

RTR (Radio Transmission and Reception function) SCF (Service control Function)

SMF (Security Management Function) TAC (Terminal Access Control function) UIM (User Identification Management function)

1.

CEC Deliverable No: AC085/INT/ACT/DS/P/035/b1

Title of Deliverable: Wireless ATM MAC – Final Report