gorithm schedules each transmission of data by L1 control signal- ing. Henceforth, this kind of PS method is referred to as fully dynamic PS. 10.4.3.1 Design Criteria of the Packet Scheduling Algorithm for VolP The following issues should be considered when designing a PS algorithm for VoIP traffic: Strict delay requirements of VoIP service -As described in Section 10.3, the tolerable air interface delay for VoIP traffic (including packet schedul- ing and buffering) should be strictly within 80 ms. When this delay is exceeded, the quality of the voice perceived by the user starts to deteriorate rapidly. Due to the stringent delay limit, time domain scheduling gains for VoIP traffic are very limited, as the buffered VoIP packet(s) should be scheduled within the given delay budget in order to sustain good speech quality. For users whose channel is in a deep fade, the delay limitation implicitly means that there is not enough time for PS to wait until the con- ditions become more favorable. Instead, the data should be scheduled early enough to allow enough time for the needed retransmissions. This implies that weak users, that is, users relying on HARQ retransmissions, should be prioritized in the user selection. Low user data rate of VoIP service The size of the VoIP packet is typically very small; for an example, for an AMR 12.2-kbps codec, the size of the most common ROHC compressed packet is 40 bytes (every 20 ms). Together with strict delay requirements of VoIP traffic, this leads to frequent transmission of small payloads, as it is not possible to wait long enough to send more than a few VoIP packets at a time. Therefore, when high capacities are targeted, it © 2009 by Taylor & Francis Group, LLC Long Term Evolution: 3GPP LTE Radio and Cellular Technology is necessary for several users' transmissions to share the DSCH resources in each TTI, and each user needs to be scheduled fairly often. Managing the control overhead-Due to the low user data rates, the number of scheduled users per TTI can become quite large