Based on IoT network security considerations, the BT mesh specification defines twice encryption for each data packets. One of the encryptions is in Network layer, it uses NetKey to separately encrypt DST (destination address) and Lower Transport PDU with AES encryption, and obfuscates SEQ (sequence number), SRC (source address), and TTL (time to live). However, the security mechanism may increase the packet process overhead of all relay nodes in mesh networks, and reduce packet forwarding efficiency. This paper will design a BT mesh routing, tag switching and adopt CRC-24 chained computing mechanisms concurrently to avoid the packet process overhead caused by the security mechanism and improve the forwarding efficiency of data packets at all relay nodes.

In IEEE 802.16 specifications, a CRC field can be attached in the rear of a WiMAX MPDU. Thus, each intermediate node (relay node or base station) in an 802.16-based multihop network can perform error detection on a received WiMAX MPDU. On the sender, the ARQ mechanism will be enabled to retransmit the MPDU if a transmission error occurs and an ACK message cannot be received. However, the ARQ mechanism is unsuitable for real-time traffic due to the delay consideration and the CRC field becomes an option to reduce the overhead of a WiMAX MPDU. Once the CRC field is removed from a WiMAX MPDU, the error occurrence cannot be detected by the intermediate nodes in time, and the erroneous data is still forwarded in the network but discarded by the destination. The resources of nodes in a network are wasted. Hence, the error detection mechanism should be retained for real-time traffic, but the overhead of CRC should be reduced. In this paper, we study an efficient discrete-error-checking scheme (DECS) to reduce the CRC overhead for real-time traffic. The DECS only needs several CRC checking bits, which are attached behind some WiMAX MPDUs. The DECS can efficiently provide the error detection for the intermediate nodes to discard these erroneous and useless data early. Thus, the utilization of node resources and wireless bandwidth can be improved significantly.

Wireless mesh networks (WMNs) is a promising technology that provides broadband wireless Internet access. It is one of the most important challenges to establish multiple connections among stations (STAs) in WMNs. In this paper, we propose a novel automatic mesh scheme (AMS) of layer 2 to form WMN in IEEE 802.11 wireless networks. AMS establishes multiple connections from a STA to neighbor STAs and determines proper routing path effectively, where three objectives are optimized, i.e., minimizing the average hop count, balancing traffic load and without modifying the communicating procedure in IEEE 802.11 standard. AMS owns self-organization capacity, establishes multiple connections and determines routing path automatically. Our AMS only uses simple software functions without the cost of extra hardware overhead. Simulation results show that the proposed scheme significantly improves the system performance. Importantly, AMS that works very well has been implemented and exhaustively tested in a realistic test-bed.

Real-time multimedia streamings on the IEEE 802.11 wireless mesh networks will be one of the popular applications. It (802.11, WiFi) adapts an acknowledgement and retransmission mechanism to provide a reliable transmission environment. To perform the mechanism, the CRC-32 field will be required and attached behind the data frame. As the data frame becomes corrupt, it will be discarded and retransmitted. However, due to the time constraint, the retransmission may be not suitable for real-time streamings anymore. Thus, the CRC-32 field may be removed to reduce overhead of a data frame. As a result, the corrupt data frames can not be found by the intermediate mesh stations (mSTAs), and are still forwarded to the destination. The wireless bandwidth is wasted. Hence, a data frame should retain a low overhead error detection field. In this paper, we propose a successively computing CRC mechanism (SCCM) to generate the low overhead field for each data frame of real-time multimedia streaming in a wireless mesh network. The field adopts a partial CRC-32 checksum, but can possess efficient error detection ability. The SCCM performs the general CRC-32 calculation, it hence can be implemented on the current hardware circuit. Using the SCCM, the corrupt and useless data frames can be found and discarded in the network early. Thus, the mSTA resources and wireless bandwidth utilization can be improved significantly.

Based on IEEE 802.16 specifications, the convergence sublayer (CS) of 802.16-based networks provides the function for heterogeneous upper layer protocols. The CS can encapsulate such as IP packets with variable lengths or ATM cells with fixed length in its MAC PDU and usually adds a CRC-32 field to the rear of the MAC PDU. Based on the CRC-32, each 802.16 relay node or BS can detect error occurrence on a MAC PDU and use ARQ mechanism to retransmit the corrupt MAC PDU. However, for real-time streaming (e.g., UDP streaming), the ARQ mechanism is not required and the CRC-32 is also removed. Once CRC-32 is removed from the MAC PDUs, PDU error will not be detected by the intermediate nodes in time and these corrupt IP packets or ATM cells will be still forwarded in the networks to waste radio bandwidth. Hence, the error detection mechanism could be maintained, but the large overhead of CRC-32 should be reduced for real-time streaming. In this paper, we propose an efficient discrete-error-checking scheme (DECS) to reduce the overhead of error detection for real-time streaming. The proposed DECS only needs a few checking bits inserted in the MAC PDU, and it can efficiently provide the error detection function. Moreover, a chase mechanism concurrently works on each relay node and BS to early discard these corrupt and useless IP packets or ATM cells. The concept of the DECS including the chase mechanism can be extensively implemented in many wire and wireless multi-hop networks to further improve bandwidth utilization.

The meta-heuristic methods, genetic algorithms (GAs), are frequently used to obtain optimal solutions for some complicated problems. However, due to the characteristic of natural evolution, the methods slowly converge the derived solutions to an optimal solution and are usually used to solve complicated and offline problems. While, in a real-world scenario, there are some complicated but real-time problems that require being solved within a short response time and have to obtain an optimal or near optimal solution due to performance considerations. Thus, the convergence speed of GAs becomes an important issue when it is applied to solve time-critical optimization problems. To address this, this paper presents a novel method, named hyper-generation GA (HG-GA), to improve the convergence speed of GAs. The proposed HG-GA breaks the general rule of generation-based evolution and uses a pipeline operation to accelerate the convergence speed of obtaining an optimal solution. Based on an example of a time-critical scheduling process in an optical network, both analysis and simulation results show that the HG-GA can generate more and better chromosomes than general GAs within the same evolutionary period. The rapid convergence property of the HG-GA increases its potential to solve many complicated problems in real-time systems

In IEEE 802.11 infrastructure wireless local area networks (IWLANs), most of data frames are transmitted between access point (AP) and wireless stations (STAs). The data transmission in IWLAN is inefficiency since the excessive overhead generated from frequent handshakes between AP and STAs and contentions among STAs. For minimizing the bandwidth wastage, in this paper, we propose a new ACK-based polling strategy to efficiently coordinate and arbitrate the sequence of transmissions among STAs. The proposed strategy alters the consecutive handshake sequence between sender and receiver defined in IEEE 802.11 medium access control (MAC) protocol to minimize the handshaking overhead and to reduce or even eliminate the potential collisions in transmissions. Different from standard handshakes, the recipient of data frame postpones sending acknowledgement (ACK) control frame to schedule the timing of the next transmission from sender. The ACK frame is sent from receiver via standard contention protocol and the sender waits the ACK frame for the authorization to send the next data frame. The simulations and analytical results demonstrate that the proposed ACK-based contention strategy is able to improve the transmission efficiency by simply reducing the overheads of handshakes and collisions in the wireless networks.