Algorithms for effective variable bit rate traffic smoothing

The transfer of prerecorded, compressed variablebit-rate video requires multimedia services to support large fluctuations in bandwidth requirements on multiple time scales. Bandwidth smoothing techniques can reduce the burstiness of a VBR(Variab1e Bit Rate) stream by transmitting data at a series of f i e d rates, simplifgzng the allocation of resources in video servers and the communication network. RCBR (Re-negotiated Constant Bit-Rate) service model seems ideally suited for smoothed V B R traffic, which is piece-wise CBR(Constant Bit Rate). Jiang [4] proposed a dynamic progmmming algorithm to compute the optimal regotiation schedule given the relative cost of renegotiation and client buffer size. We show that the renegotiation schedule produced by his algorithm has high peak rates and frequent renegotiations. We propose another algorithm that wmputes a renegotiation schedule that has a slightly higher cost than the optimal schedule, but has other desirable properties, such as lower peak rate and lower frequency of renegotiations. We also consider proxy-based online smoothing, and propose an adaptive heuristic algorithm to generate renegotiation schedules at runtime without knowledge of future frame size infomation. We compare the schedule computed by the algorithm to the optimal schedule computed with full knowledge of future frame sizes.