2. 1 Introduction Objective —Improve the efficiency for transmitting small packets to multiple users —Support for low data rate/real-time applications such as Voice over IP Multi User Frame Description —Modified preamble structure for the encoder packets allows the partially filled encoder packets to one multiplex other user’s data if available and/or transmit at a lower data rate to improve the FER —Multiplex up to 4 users in one frame for transmitting high data rates —Reduce the maximum HDR physical layer packet size from 512 bytes to 128 bytes

3. 2 HDR Preamble Structures For data rate >= 1.2288 kbps, the traffic payload for the high data rate encoder packets can be shared among several users Each user may receive one or more FTC packets In this case, the preamble has ‘head room’ to support more than one AT ID HDR Frame Structure

4. 3 Modified Preamble Structure For transmission data rate < 1.2288 Mbps, maintain the HDR preamble structure For transmission data rate >= 1.2288 Mbps, we propose change the preamble length to 128 chips, and divide it into the several fields Preamble Duration Modulation Phase EDRI I2I2 I1I1 Q1Q1 Q2Q2 Null I- Branch Q- Branch 32 chips 64 chips

5. 4 Explicit Data Rate Indicator (EDRI) EDRI is only set when the transmission rate is 1.2288 Mbps or higher. For lower data rate, HDR preamble (MAC identifier on I channel) will be used EDRI is (8,4,4) bi-orthogonal coded and block repeated 8 times EDRI specifies one of the following rate: 1.2288 Mbps, 1.8432 Mbps, 2.4576 Mbps If a user requests DRC >= 1.2288 Mbps, and EDRI is set, then the user have to check the MAC Identifiers to see if the packet is for him

6. 5 MAC Identifiers I 1,I 2,Q 1,Q 2 are 32-ary Walsh coded MAC Identifiers

7. 6 Multi-User Frames for Data Rates >=1.2288Mbps Assign FTC Packets destined to one or more ATs to an Encoder Packet such that the data rate requested by each AT is > or = the data rate of the Encoder Packet. —Note: In the event FTC packets are only available for a single AT, then transmit an Encoder Packet at the lowest data rate capable of transporting the available FTC packets. This maintains throughput while improving the Encoder Packet error rate. –For example: Transmission is scheduled for an AT. The data rate requested by the AT is 2457.6 kbps and the queue for this AT contains 2 FTC Packets. No other FTC packets are available for multiplexing. Then the 2 FTC Packets are transmitted in an Encoder Packet at 1228.8 kbps.