WiMAX TLV Encoding Format Explained

This document describes the WiMAX TLV encoding format. In WiMAX, TLV formats are used for parameters within MAC management messages as well as configuration files.

TLV stands for Type, Length, and Value.

• The size of the Type field is always 1 byte.
• The size of the Length field can be either 1 byte or more than 1 byte. The size of the Value field depends on the specified Length field.

Length Field Encoding Rules

Here’s how the length field is encoded:

Case 1: Value Field Size <= 127 Bytes (Length <= 127)

• The size of the Length field will be 1 byte.
• The Most Significant Bit (MSB) of the Length field is set to zero (0).
• The remaining 7 bits of the Length field indicate the actual size of the Value field in number of bytes.

Example: FEC (Forward Error Correction) code type for downlink burst: 150 (0x96), 0x01 (msb:0), 0x01 (QPSK 1/2)

• First byte (0x96) is the Type.
• Since the value is less than 127 bytes, the Length field (0x01) is one byte with the MSB set to zero. The remaining 7 bits indicate that the size of the Value field is one (1) byte.
• The Value field (0x01) represents QPSK 1/2 modulation-code rate.

Case 2: Value Field Size > 127 Bytes (Length > 127)

• The size of the Length field shall be one byte more than what is actually used to represent the size of the Value field in bytes.
• The MSB of the first byte of the Length field is set to one (1).
• The remaining 7 bits of the first byte of the Length field indicate the number of additional bytes in the Length field.
• The bytes other than the first byte of the Length field are used to represent the size of the Value field.

Example: Frequency (Uplink center) of value 2400000 KHz (i.e., 2.4 GHz):

• Type = 5 (0x05)

• Length = 0x83, 0x00, 0x00, 0x03

  In the first byte (0x83), the MSB is set to 1. The remaining 7 bits indicate that there are 3 additional bytes in the Length field. The second, third, and fourth bytes (0x00, 0x00, 0x03) together represent the size of the Value field (i.e., the actual frequency value), which is 3.

• Value = 0x249F00