Wireless multi-hop sensor networks consist of a wired backbone network, gateway nodes and wireless sensor nodes. To resolve the bottleneck problems in the neighborhood of the gateway node, we propose an effective carrier sensing multiple access algorithm based on a distributed bottleneck alleviation (DiBA) scheme. Using the concept of a relay token, we utilize a linear distribution as the probability density functions for the selection of backoff counter value, rather than using a uniform distribution. From simulation results, we show that system throughput and user fairness are remarkably improved in random topology compared with conventional schemes.