8.6 TLV Encoding in the 802.16 Standard

A TLV encoding consists of three fields (a tuple): Type, Length and Value. TLV is a formatting scheme that adds a tag to each transmitted parameter containing the parameter type and the length of the encoded parameter (the value). The type implicitly contains the encoding rules. TLV encoding is used for parameters in MAC management messages. It is also used for configuration, definition of parameters like software updates, hardware version, Vendor ID, DHCP, etc.

The length of the Type field is 1 byte. The lengths of the remaining fields is explained in the following.

If the length of the Value field is less than or equal to 127 bytes, then the length of the Length field is 1 byte, where the most significant bit is set to 0. The other 7 bits of the Length field are used to indicate the length of the Value field in bytes.

If the length of the Value field is more than 127 bytes, then the length of the Length field is one byte more than is needed to indicate the length of the Value field in bytes. The most significant bit is set to 1. The other 7 bits of the first byte of the Length field are used to indicate the number of additional bytes of the Length field (i.e. excluding this first byte). The remaining bytes (i.e. excluding the first byte) of the Length field are used to indicate the length of the Value field.

Disjoint sets of TLVs are made that correspond to each functional group. Each set of TLVs that are explicitly defined to be members of a compound TLV structure form an additional set. Unique Type values are assigned to the member TLV encodings of each set. Uniqueness of TLV Type values is then assured by identifying the IEEE 802.16 entities (MAC management messages and/or configuration file) that share references to specific TLV encodings.

8.6.1 TLV Encoding Sets

In Table 8.7, a brief description is given of TLV encoding sets in the 802.16 standard. For each encoding set, the section of the standard is given where details of this encoding can be found. For some TLV sets, the standard defines TLV encoding parameters for each PHY specification.

Table 8.7: Brief descriptions of TLV encoding sets in the 802.16 standard. Several Type values are common to different sets but no confusion is possible
Open table as spreadsheet
Encodings set	Type	Description
Common encodings	143→149	Define parameters such as current transmit power, downlink/uplink service flow descriptor, HMAC (see Chapter 15) information, etc. Some of these parameters are used by the other TLV encodi ng sets. Section 11.1 of the standard
Configuration file encodings	1→7	Only for the configuration (Section 9 of the standard). Define parameters like software updates, hardware version, Vendor ID, etc. Section 11.2 of the standard
UCD management message encodings	1→5	Define uplink parameters such as the uplink burst profile that can be used (see Chapter 9). Section 11.3 of the standard
DCD management message encodings	1→17	Define downlink parameters such as the downlink burst profile that can be used (see Chapter 9). Section 11.4 of the standard
RNG-REQ management message encodings	1→4	Define Ranging Request parameters such as the requested downlink burst profile. Section 11.5 of the standard
RNG-RSP management message encodings	1→13	Define ranging response parameters. Example: Basic CID and Primary management CID are TLV RNG-REQ encoded parameters. Section 11.6 of the standard
REG-REQ/RSP management message encodings	1→17	Define Registration Request parameter:'s such as CS capabilities, ARQ parameters, etc. (see Chapter II). Section 11.7 of the standard
SBC-REQ/RSP management message encodings	1→4	Define SS Basic Capability Request parameters such as physical parameters supported and handwidth allocation support (see Chapter II). Section 11.8 of the standard
PKM-REQ/RSP management message encodings	6→27 except 14, 25 and 26	Define security-related parameters like SAID (Security Association IDentifier), SS certificate, etc. (see Chapter IS) Section 11.9 of the standard.
MCA-REQ management message encodings	1→6	Define Multicast Assignment Request parameters like Multicast CID, periodic allocation type. etc. Section 11.10 of the standard
REP-REQ management message encodings	1	Define parameters related to channel measurement report request. Section 11.11 of the standard
REP-RSP management message encodings	1 and 2	Define parameters related to channel measurement report which is the response to channel measurement report request. Section 11.12 of the standard.
Service flowmanagement encodings	1→28 except 4 and 27, 99→107 and 143	Define the parameters associated with uplink/ downlink scheduling for a service flow like SFID, CID, etc. Section 11.13 of the standard

In this table, it can be verified that the Type values of common TLV encoding sets are unique (when compared to other sets). This is the only collection for which global uniqueness is guaranteed.

Annex B of this book provides a detailed example of TLV coding use in 802.16.