In this paper, we propose an improved TCP scheme, TCP BRJ, which is capable of adjusting the initial slow-start threshold and congestion window in real time according to the bandwidth estimation in slow-start phase, dividing the network congestion grades based on round-trip time (RTT) jitter in congestion avoidance phase, distinguishing the random packet losses from the congestion packet losses, and reacting accordingly. Simulation results by NS-2 show that TCP BRJ provides more significant performance improvement in throughput, bandwidth utilization and fairness than TCP Reno and TCP Westwood in heterogeneous networks with high random bit-error rate (BER), and shows friendliness towards the widely used algorithm TCP Reno.