Browse Prior Art Database

Grouping Multiple Users into a Single Packet with TxAA

IP.com Disclosure Number: IPCOM000126481D
Original Publication Date: 2005-Jul-20
Included in the Prior Art Database: 2005-Jul-20
Document File: 2 page(s) / 64K

Publishing Venue

Motorola

Related People

Sean McBeath: AUTHOR [+5]

Abstract

In some wireless communications systems, multiple users are served together in a single packet. This is potentially problematic for systems employing antenna weighting schemes such as transmit adaptive arrays (TxAA) [1], since different users require different weights for optimum performance. In this paper, we propose seven rules for assigning weights for a transmission for multiple users based on the feedback from a set of the users. The rules allow for efficient operation of schemes that employ antenna weighting for multiple user transmissions.

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Grouping Multiple Users into a Single Packet with TxAA

By Sean McBeath, Doug Reed, Jack Smith, Danny Pinckley, and Rob Nikides

 

ABSTRACT

In some wireless communications systems, multiple users are served together in a single packet.  This is potentially problematic for systems employing antenna weighting schemes such as transmit adaptive arrays (TxAA) [1], since different users require different weights for optimum performance.  In this paper, we propose seven rules for assigning weights for a transmission for multiple users based on the feedback from a set of the users.  The rules allow for efficient operation of schemes that employ antenna weighting for multiple user transmissions.

PROBLEM

The latest release of the cdma2000 High Rate Packet Data (HRPD) Air Interface Specification [2] includes a method to serve multiple users in a single packet.  This method is know as Medium Access Control (MAC) layer multiplexing and can facilitate up to 8 users in one packet.  These multi-user packets allow HRPD to be more effective, when compared to previous versions of HRPD, in delivering real time applications such as voice, video, and gaming due to the latency improvement.  Since the multiplexing is in the time domain before the packet is coded, all access terminals (ATs) for which the packet is targeted must successfully decode the packet before the access network (AN) can cease transmitting the packet.  Thus, early terminations are less likely.

For a system employing transmit adaptive arrays (TxAA) or switched transmit diversity (STD), each AT sends its optimum TxAA weights (antenna gains and phase relationship) to the AN.  This scenario is depicted in Figure 1, where four ATs are reporting their optimum TxAA weights, namely v1 and v2 to the AN.  Different TxAA weights are optimum for different users.  However, for a transmission for multiple users, only one TxAA weight can be applied for the entire group of users.  For example, consider that the four ATs in Figure 1 are to be served together in one multi-user packet.  Each AT requests its optimum antenna weight (v1 and v2), but the AN can only serve the set of four users using one antenna weight (v1 and v2).  Therefore, a method needs to exist which establishes rules for multiplexing users into packets which have varying TxAA weights.

Figure 1

SOLUTION

In this paper, we propose that a set of rules be established when using TxAA and multi-user packets.  In particular, the AN takes a set of requested TxAA weights and assigns users to packets and then assigns a given TxAA weight to optimize performance.

OPERATION

We propose that the following rules be used to group multiple users into packets while considering the TxAA weights requested by the AT.

1.        Initially, the AN will examine the set of TxAA weights and data rate control (DRC) information from all ATs in the system.  The AN would then group users which have the same TxAA weights and compatible DRC values into one multi-user packet. ...