hannel quality reports from the MS help the BS scheduler adjust the throughput and latency of the uplink and downlink transmissions corresponding to a certain MS (see Figure 6-23). The BS scheduler may or may not coordinate the downlink and uplink transmissions to a mobile station with other base stations. The inter-BS coor- dination is required in certain deployment scenarios (e.g., interference management and coordination) or MIMO schemes (e.g., multi-BS MIMO or DL/UL multi-point coordinated transmission in 3GPP LTE-Advanced). The scheduler decisions are signaled to the MS through allocation A-MAPs (DL/UL MAPs in the legacy systems) for the downlink and uplink. Figure 6-23 shows an example operation of the BS scheduler in the downlink and uplink. Depending on the type of application layer services, the service flows are classified and assigned QoS parameters, and are then mapped to downlink or uplink connections. The IEEE 802.16 standard does not define a scheduling algorithm, and the details of scheduler implementation remain proprietary and vendor-specific. However, there are certain scheduling algo- rithms such as Round Robin, Weighted Round Robin, Proportional Fair (PF), Weighted Proportional Fair, etc., that are typically used. The details of the weighted proportional fair algorithm are provided in Appendix A of this chapter. The MAC protocol peers communicate using a set of MAC control messages. These messages are defined based on ASN.1 syntax. The Packed Encoding Rules (PER)xvi are used to encode the messages XviPacked Encoding Rules (PER) are ASN.1 encoding conventions for producing compact transfer syntax for data struc- tures described in ASN.1. CHAPTER 6 The IEEE 802.16m MAC CPS (Part I) MS CQI Reports (Narrowband/ Wideband SINR Measurements) Resource Allocation (Burst size, Modulation and Coding, MIMO MS Bandwidth Request Scheduler Parameters, etc.) MS/Service Flow QoS Requirements and Parameters BS Scheduler Operational Concept Video- Video -HTTP- nrtPS nrtPS E-Mail- E-Mail UL MAP BS Scheduler Func