Monir Hossen

An efficient multi-OLT and multi wavelengths passive optical network for differentiated classes of services

Passive optical network (PON) is getting more popularity because it provides large bandwidth, uses only passive components that requires less power consumption, highly dynamic access network, and effectively converges several service providers. With the increase of multiple users having different priority classes of services an efficient access network is required which can handle the different data classes with better quality of services (QoSs). Usually, a single optical line terminal (OLT) and single wavelength (SS) PON is capable to provide multiple services and applications such as IPTV, HDTV, video conferencing, and real-time data transmission. However, the SS-PON is not the best network architecture to maintain better QoSs for all those services because it requires a complex dynamic bandwidth allocation (DBA) algorithm and synchronization of local time those lead a large delay. To overcome those problems in SS-PON, in this paper, we propose an efficient PON architecture which consists of two OLTs and two uplink wavelengths, i.e., multi-OLT and multi-wavelengths PON (MM-PON), for different classes of services. Here, two OLTs are used to reduce the data processing complexity and two uplink wavelengths are used to transmit the three different priority classes of services defined by IEEE802.1D standard. This paper presents a new network structure of MM-PON with simulation results for modified limited service DBA algorithm to prove the validity of the proposed network architecture. The simulation results show that the MM-PON with strict priority scheduling provide less packet delay, reduce the probability of packet loss, remove light load penalty, and maintain service level agreements for each priority class of service than the conventional SS-PON.

Thread guaranteed algorithm for real time traffic in multi-threaded polling of PON-based open access network

Open access network (OAN) is an efficient converged network that can effectively connects several service providers in a ubiquitous city (u-City). Passive optical network (PON) provides enough bandwidth to support huge data traffic of the modern OAN of u-City. However, some service providers in the u-City contain high priority (HP) traffic while other service providers comprise low priority traffic, i.e., best efforts (BE) traffic. This HP traffic means the real time traffic, e.g., voice over internet protocol (VoIP), IPTV, video on demand (VoD), video conferencing etc. The conventional polling algorithms of the PON cannot provide differentiated service for data traffic of different priority groups. These polling algorithms also require almost same back off delay for both the HP and BE data traffic. So the PON-based OAN with the conventional polling algorithms are not enough to provide the real time service for the HP traffic. In this paper, we propose a new multi-threaded dynamic bandwidth allocation (DBA) algorithm for the PON-based OAN that provides lower delay for the HP traffic by reducing the back off delay in every polling cycle. The proposed algorithm is called thread guaranteed bandwidth allocation (TGBA) algorithm. Performance of the proposed TGBA algorithm is evaluated by numerical simulations in terms of end-to-end packet delay and pre-transmission delay. The proposed scheme provides lower end-to-end and pre-transmission delays for the HP traffic than those of the conventional single-threaded and multi-threaded DBA schemes.

Energy balanced protocol for ensuring equal lifetime of every node of wireless sensor networks

Wireless sensor networks (WSNs) give us the opportunity to monitor a variety of real time environmental conditions and it helps to make our lifestyle modernized. Usually, every sensor node (SNd) consists of a small battery which is difficult to recharge. The main problems with this WSN are to provide longer lifetime and to maintain the energy consumption level equal for every SNd. When SNds are deployed either with random or predefined manner in an impregnable area for monitoring environment then it must necessary to ensure the same lifetime for every node. In this paper, we study the problems of reducing energy consumption and ensuring the equal power level for all nodes. Our focus is to design a new protocol that can balance the energy consumption among all the SNds in a WSN. With considering all possible cases to make the scenario more realistic, we develop a new energy balancing protocol that uses adaptively variable hop distance from the boundary to the coordinator nodes. Simulation result shows that the proposed method can provide much better performance compared to the existing protocols in both best and worst case scenarios of WSN.

Modified hybrid slot-size/rate DBA algorithm for improving quality of services of high priority data packets of PON system

Nowadays, real time data transmission, i.e., high priority (HP), over internet is very popular. That is why, Ethernet passive optical networks (EPONs), with the properties of low cost, high speed and high efficiency with quality of service (QoS) have become promising candidates for the next generation broadband access network. To avoid data collision and provide effective bandwidth utilization a medium access control protocol is mandatory to share the resources in the upstream transmission medium. This paper presents a new dynamic bandwidth allocation algorithm (DBA) which is the modified version of the hybrid slot-size/rate (HSSR) DBA scheme. In the HSSR scheme, total transmission window of a time cycle is divided into two parts, where 1st part is steadily divided among the optical network units (ONUs) of the network and used for the HP data traffic. This bandwidth distribution is fixed and does not depend on the traffic size in the queue of the ONUs. In contrast, in the proposed scheme, the 1st part of the transmission window is dynamically distributed to all the ONUs according to the bandwidth demand of the HP traffic of each ONU. The 2nd part of the transmission window is dynamically allocated for the BE traffic of one or multiple ONUs in both the existing HSSR and proposed schemes. The performance of the proposed scheme has been compared to the existing HSSR scheme in terms of end-to-end packet delay and bandwidth utilization. Our proposed scheme provides better bandwidth utilization and lower end-to-end packet delay for the HP data traffic in the network.

Control message scheduling algorithm for improving throughput and jitter performance of the MHSSR DBA scheme of PON

Ethernet passive optical network (EPON) is ratified widely as access network for its superfluous bandwidth to deliver multiple services and applications, such as voice communications, standard and high-definition videos (SDTV and HDTV), video conferencing (interactive video), real-time and near-real-time data traffic. To support these applications, huge number of algorithm so far developed and modified hybrid slot-size/rate (MHSSR) DBA algorithm is one of them. In this paper, we have proposed new control messages scheduling schemes of the multi-point control protocol for the MHSSR DBA algorithm. We have performed numerical simulation to evaluate the performance of the proposed scheme in terms of throughput, number of remaining data bytes and jitter performance for different offered loads and cycle times. The proposed scheme outperforms than the existing HSSR scheme for all the above performance parameters.

An algorithm for reduction of packet delay and waiting time for unstable ONUs in PON

Passive optical network (PON) is a highly dynamic access network that effectively converges several service providers. In a time cycle, some optical network units (ONUs) of a PON may miss the usual polling instant. In that case, the ONUs those miss the usual polling instants are called unstable ONUs. According to the existing early dynamic bandwidth allocation (E-DBA) algorithm, once an ONU miss the usual polling instant it needs to be waited until the end of upstream transmissions from the entire stable ONUs in the PON. That is why, the unstable ONUs suffers from more waiting time than the stable ONUs of a PON. This paper proposes a new DBA algorithm called modified E-DBA (ME-DBA) algorithm, for reduction of waiting times of the unstable ONUs in the PON. In the proposed ME-DBA algorithm, total ONUs in a PON are divided into several small groups. The data packets from all the stable ONUs of a group are transmitted 1st and then the data packets from the unstable ONUs of that group are transmitted. We have analyzed and compared the performance of the proposed ME-DBA algorithm with the existing E-DBA algorithm in terms of the average packet delay and waiting time of the unstable ONUs by using computer simulations. The simulation results show that the proposed algorithm provides lower end-to-end packet delay and waiting time for the unstable ONUs than that of the existing E-DBA algorithm.

A routing protocol for improving energy efficiency in wireless sensor networks

Wireless sensor network will get wide applicability and acceptance if improved energy efficient routing protocol is implemented. Most of the cluster based hierarchical routing protocols use base station (BS) as a main controller to select cluster heads (CHs) which increases energy consumption and round trip time delay. In this paper, we propose an improved energy efficient routing protocol to maximize the network life time and reduce data delay time. In this proposed protocol, new CH is selected by the current CH instead of the BS based on the maximum residual energy and minimum distance between the CH and a node among all the nodes in a cluster. Unlike the modified LEACH (MLEACH), in the proposed protocol re-clustering is occurred only when the residual energy of the current CHs lower than a threshold value. From the comparison of the simulation results it is proved that the proposed protocol provides lower cluster formation time and network failure with better network fault tolerance and packet delivery ratio than the MLEACH.

Online multi-thread polling algorithm with predicted window size for DBA in long reach PON

Passive optical network (PON) has become the vital technology for the next generation access networks. The advancement of optical technology extends the span of the PON from 20 to 100 km. Such an extended PON is known as Long-Reach PON (LR-PON). But the data transmission in the existing LR-PONs suffer from longer propagation delays between the optical line terminal (OLT) and optical network units (ONUs) that degrade the performance of the traditional dynamic bandwidth allocation (DBA) algorithms in the upstream bandwidth allocation of the LR-PONs. This challenge is the main reason to propose a new algorithm which can reduce the effect of longer propagation delay, i.e., due to larger round trip time (RTT), between the transmission of Report messages from the ONUs and reception of Gate messages from the OLT in the LR-PONs. This proposed algorithm allocates some additional bandwidth based on the prediction during the RTT between the OLT and ONUs if the requested bandwidth is less than the maximum bandwidth of the ONUs. The proposed algorithm is a modified version of the existing online multi-thread polling algorithm. The proposed prediction based online multi-thread polling algorithm reduces the end-to-end packet delay and increases the bandwidth utilization and throughput significantly than any other centralized DBA algorithms which are proposed for the LR-PONs.