| Wireless LAN are gradually directing towards to multi-chain and multi-radio. With the number of antenna and radio increased, the band width of network expanded. However, it requires more and more power to obtain higher transmission speed. Hence, those operators who operate wireless local area network need to consider that tens of millions new Access Point(AP) devices cause huge energy consumption. Therefore, this paper studies power saving strategies for multi-radio multi-chain AP is significant.Firstly, this paper analyzes the key technologies of the IEEE 802.11 n standard, and on basis of energy consumption evaluation model is proposed for multi-radio multi-chain 802.11 n AP device. According to the principle of CSMA/CA, network equipment is divided into the four operating modes, which included of "transmitting", "receiving", "idle-listening" and "sleeping". Secondly, the OPNET simulation platform is established by this paper, and this paper describes the simulation model design, including network model, node model, process model, the pipeline model and energy statistics module in detailed. Thirdly, built on the simulation platform this paper makes a series of simulations of the key factors affecting the AP energy consumption, including traffic load, signal to noise ratio(SNR), modulation and coding scheme(MCS), spatial stream(SS), bands and business diversion proportion. Simulation results show that 1) when the network traffic load is below a certain transmission threshold, the antenna of the AP can be downgraded. This threshold depends on signal to noise ratio(SNR), where terminals distribute. with SNR increased, the threshold increased, vice versa. 2) When single band can’t meet the current rate of the traffic sources and the extra energy transmission business is more than offset the cost of operating a new band, that start the dual-band split has the most energy efficient.After studying the pivotal factors of affecting the network energy consumption, this paper proposes power saving schemes for multi-radio MIMO 802.11 n AP device, in order to achieving more systematic and obtaining operability in practical applications. The core modules of the energy-saving programs contains antenna downgrade algorithm and the conversion between single and dual band. All of those are based on online sampling, perform real-time network statistics and select the most energy efficient antenna and band configuration adaptively. The antenna downgrade means to turn down one of more transmission chain to save power consumption, when a single antenna cansatisfy the requirement of quality of service(Qo S). This algorithm can be designed in transmit and receive side. Similarly, the conversion between single and dual band also means that when the single-band can meet the demand of Qo S, only one radio should be turned on, otherwise double radios should be opened. Followed above, this paper analyzes four traffic splits schemes and proposes our scheme which combines the advantage of water-filling method and frame aggregation for improving the EE further. At the beginning, an incoming packet should be put into a funnel equipped with a piston. When the weight of a funnel exceeds a pre-defined threshold, all the packets in that funnel should be delivered over an active radio.Finally, this paper performs simulation tests for the schemes of the antenna downgrading and frequency band conversion. Simulation results show the our proposed algorithms can achieving the optimal energy-efficient radio and chain configuration, with guaranteeing the network throughput and latency performance under the premise to meet the requirement of users. In addition, compared with the other split schemes, our proposed scheme has the better network performance and energy efficiency gains. |
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