Broadcasting is one of the basic data transmission methods in wireless ad-hoc networks, used for various purposes including fundamental network operations, service discovery, route discovery and even actual data transmission. The efficiency of broadcast protocol relies on several factors viz. number of forwarding stations, reliability, fault-tolerance ability, energy consumption, scalability and reachability. All neighbor knowledge-based reliable broadcast protocols can generally be categorized into proactive and reactive approaches. In proactive approach, a station creates forward list from its one-hop neighbors and announces the forward list by appending it into the packet header during broadcast. Whereas, in reactive approach, a station does not need to create such forward lists but decides by itself whether to forward or not. Although the proactive protocols show better performance than reactive protocols in minimizing number of forwarding stations due to use of extended neighbor information. However, appended forward list and extended neighbor information increase overhead and consume more network resources. Thus, the proactive broadcast protocols becomes non-scalable for large and sparse network. To design an efficient broadcast protocol, we are motivated from timer mechanism of a reactive protocol named scalable broadcast algorithm (SBA). The key shortcomings of SBA is probabilistic timer mechanism that selects a timer counter value for a station randomly from timer ratio which is determined by considering static neighbor information of the station. In this paper, a deterministic timer mechanism-based scalable broadcast protocol named improved scalable broadcast algorithm (I-SBA) is proposed to solve these issues. However, this protocol suffers from slightly bounded broadcast delay than flooding and self-pruning, it significantly reduces number of forwarding stations. The simulation results prove that I-SBA is an efficient protocol since it shows better performance in number of forwarding stations, saved rebroadcast, redundancy, and energy consumption than other reactive protocols.