Simone
Building a networked control system over wireless is a challenging task. The scarce spectrum imposes a fundamental limit on the performance of the wireless channel.Random delays and packet losses are inevitable建立网络化的无线控制系统是一个极富挑战性的任务。频谱资源的稀缺对无线信道的工作性能带来了很大的限制。随机延滞和数据包丢失是不可避免的。Even though this is true for any communication network, it is much more pronounced in wireless networks due to limited spectrum and power, time-varying channel gains and interference. 尽管在任何通讯网络中都会出现类似问题，但在无线网络中，由于频谱资源和功率的限制，以及随时间变化的信道增益和干扰等原因，使这个问题显得尤为突出。Besides the design challenges in the link layer,multiple transmitter and receiver pairs need to share the channel and an efficient channel access mechanism needs to be designed.除了好数闷数据链路层设计具有友弯难度之外，由于多个发射机-接收机都需要共享该信道，因毕困此还需要设计一个有效的信道接入机制。As we shall see, random access without centralized control can waste a great deal of the scarce resources in the network.我们应该看到，只有随机接入而无集中控制，会浪费网络中大量的稀缺资源。
