Body Area Network (BAN) is an important component for remote healthcare and health monitoring, and existing research often utilizes electromagnetic wave transmission for data transfer within the network. In contrast, ultrasound wave propagation in human soft tissue experiences less attenuation and generates less heat. Compared to electromagnetic wave transmission, ultrasound-based communication and networking within the human body have certain advantages, such as longer transmission distances and lower risks of inducing pathogenic effects. The existing ultrasonic wideband communication technology often uses ultra-short pulse to reduce path overlapping and the resulting interference. Besides, the multiple access through channel sharing can be realized by combining direct sequence spread spectrum. However, the interference caused by the increase of communication number reduces the received signal-to-noise ratio. Communication reliability can not be guaranteed with the fixed frame length and code length. In this paper, the adaptive rate adjustment of multiple access was modeled mathematically and the implementation methods based on competition and cooperation were studied. Then the close form solution was derived with the Lagrange multiplier method in convex optimization theory, with which the frame length and code length were dynamically changed to realize rate adjustment. Simulation results show that those methods can adapt to the changes of communication links and the resulting interference; the cooperative method based on bargaining game theory can obtain better network performance by balancing the communication rate of different access nodes; the competition scheme based on the maximum rate is helpful to improve the effective communication rate of the target communication link. In practical application, scheme should be selected according to the application scenario.