On ARQ feedback intensity of the IEEE 802.16 ARQ mechanism

The IEEE 802.16 standard defines the ARQ mechanism as a part of the MAC layer. The functioning of the ARQ mechanism depends on a number of parameters. The IEEE 802.16 specification defines them but it does not provide concrete values and solutions. We ran simulation scenarios to study how the ARQ feedback intensity impacts the performance of application protocols. The simulation results reveal that a low ARQ feedback intensity results only in a marginal improvement. Though it is possible to optimize the ARQ feedback intensity, it is reasonable to rely upon more frequent ARQ feedback messages as they do not result in a performance degradation. At the same time, ARQ connections, which work on…

Analysis of duplexing modes in the IEEE 802.16 wireless system

The IEEE 802.16 standard defines two main duplexing modes: Time Division Duplexing (TDD) and Frequency Division Duplexing (FDD). The FDD can be divided further into Full-FDD (F-FDD) and Half-FDD (H-FDD). F-FDD requires full duplexing support from subscriber stations and works with two frequency bands. TDD operates a single frequency band, but it does not need full-duplexing support. H-FDD is a combination of these: it works with two frequency bands and does not require full-duplexing support. The cost of this is a more complicated scheduling and added overhead. Still, H-FDD might be the only possible duplexing mode in some occasions. In this paper, these duplexing modes are compared and the…

Multi-Connectivity in 5G and Beyond Non-Terrestrial Networks

The Fifth Generation (5G) communications systems aim to serve such service classes as Ultra-Reliable Low Latency Communications (URLLC), enhanced Mobile Broadband (eMBB), and massive Machine-Type Communications (mMTC). To meet the growing requirements posed to mobile networks, satellites can be used to complement the Terrestrial Networks (TNs). To increase the efficiency of the satellite communications involved, bandwidth-efficient techniques should be used. Multi- Connectivity (MC) is one such technique. In MC, a User Equipment (UE), for example, a smartphone, can be connected to multiple Next Generation Node Bs (gNBs) simultaneously. In this paper, an adaptive MC activation scheme for thr…

Multi-Connectivity for User Throughput Enhancement in 5G Non-Terrestrial Networks

To meet the increasing throughput and reliability demands, satellites may be used to complement the Fifth Gener-ation (5G) Terrestrial Networks (TNs). To increase the efficiency of the satellite communications involved, research on bandwidth-efficient techniques is needed. Multi-Connectivity (MC), where a user can be connected to multiple Next Generation Node Bs (gNBs) simultaneously, is one of such techniques. In this paper, the focus is on MC in NonTerrestrial Networks (NTNs) to improve users' experienced throughputs. First, a study of relevant specifications and algorithms is conducted. Then, the designed load-aware Secondary Node (SN) addition and traffic steering algorithms are present…

Performance Evaluation of the IEEE 802.16 ARQ Mechanism

The IEEE 802.16 technology defines the ARQ mechanism that enables a connection to resend data at the MAC level if an error is detected. In this paper, we analyze the key features and parameters of the ARQ mechanism. In particular, we consider a choice for the ARQ feedback type, a scheduling of the ARQ feedbacks and retransmissions, the ARQ block rearrangement, ARQ transmission window and ARQ block size. We run a number of simulation scenarios to study these parameters and how they impact a performance of application protocols. The simulation results reveal that the ARQ mechanism plays an important role in transmitting data over wireless channels in the IEEE 802.16 networks.

Link Adaptation Thresholds for the IEEE 802.16 Base Station

The IEEE 802.16 technology defines a number of modulation and coding schemes that the base station can use to achieve the best tradeoff between the spectrum efficiency and the resulting application level throughput. However, the 802.16 specification does not define any particular link level adaptation algorithm, neither does it specify the SNR thresholds to switch between modulation and coding schemes. In this paper we consider a link adaptation model and conduct a number of simulation runs to find transition thresholds for ARQ and HARQ retransmission mechanisms. All the simulations are done with the 802.16 extension for the NS-2 simulator.

Optimal MAC PDU Size in IEEE 802.16

In the IEEE 802.16 the number of errors and the MAC PDU size have an impact on the performance of the network. We present a way to estimate the optimal PDU size and we run a number of simulation scenarios to study these parameters and how they impact on the performance of application protocols. The simulation results reveal that the channel bit error rate has a major impact on the optimal PDU size in the IEEE 802.16 networks. Also, the ARQ block rearrangement influences the performance.

PHY and MAC layer performance optimization of the IEEE 802.16 system

WINSE: WiMAX NS-2 extension

IEEE 802.16 standard defines the wireless broadband technology called WiMAX. When compared to other wireless technologies, it introduces many interesting advantages at PHY, MAC, and QoS layers. Heavy simulations are needed to study IEEE 802.16 performance and propose further enhancements to this standard. Link level simulations are not always sufficient, while system level simulators are not always accurate to capture MAC and transport protocol details. We implemented a 802.16 extension for the NS-2 network simulator. It includes upper PHY modeling, almost all the features of the 802.16 MAC layer, as well as the QoS framework. This article describes the implemented features, simulation meth…

Analysis of the Non-Transparent In-Band Relays in the IEEE 802.16 Multi-Hop System

This paper presents extensive dynamic simulations of the non-transparent in-band relays working in the distributed scheduling mode. The simulation results show that in-band relays can improve noticeably the spectral efficiency without acquiring an additional radio spectrum. Also, packet transmission delays become smaller. An important outcome of the dynamic simulations is that it is very crucial to choose a correct relay zone size where the base station and relay nodes exchange data. Otherwise, throughput fairness of the whole system declines. It indicates an importance of the relay zone size adjustment algorithm that the base station must run.

Handover performance in the IEEE 802.16 mobile networks

The IEEE 802.16 standard provides a full mobility support for stations moving across cell borders. In addition, the WiMAX Forum Network Working Group defines a set of procedures to support handovers in the mobile access network. One of the main characteristics of mobility support is fully controlled and optimized handover (HO), in which a mobile station (MS) migrates from the air interface of one base station (BS) to another one. It is vital to keep the BS transition phase as short as possible to decrease delays and data loss, which is especially crucial for real-time applications, such as VoIP. In this paper we analyze ASN-anchored mobility performance and provide advisable handover relate…

ARQ parameters for VoIP in IEEE 802.16 networks

IEEE 802.16 standard defines two data retransmission mechanisms. HARQ provides fast retransmissions in cost of slightly increased overhead. On the contrary, ARQ has less overhead in cost of bit longer delays. It is therefore often used with BE connections. In addition to delay tolerant applications, BE can also be used for real-time services. Therefore, in this paper we analyze the ARQ mechanism and provide guidelines on how to set the ARQ parameters to achieve a good balance between the VoIP delay and packet loss.

Performance analysis of the ieee 802.16 arq mechanism

The IEEE 802.16 technology defines the ARQ mechanism that enables a connection to resend data at the MAC level if an error is detected. In this paper, we analyze the key features and parameters of the 802.16 ARQ mechanism. In particular, we consider a choice for the ARQ feedback type, an algorithm to build block sequences, a scheduling of the ARQ feedbacks and retransmissions, the ARQ block rearrangement, ARQ transmission window and ARQ block size. We run a number of simulation scenarios to study these parameters and how they impact a performance of application protocols. The simulation results reveal that the ARQ mechanism and its correct configuration play an important role in transmittin…

Analysis and Performance Evaluation of the IEEE 802.16 ARQ Mechanism

The IEEE 802.16 standard defines the ARQ mechanismas a part of the MAC layer. The functioning of the ARQmechanism depends on a number of parameters. The IEEE802.16 specification defines them but it does not provide concrete values and solutions. This paper studies the key features and parameters of the 802.16 ARQ mechanism. In particular, we consider a choice for the ARQ feedback type, an algorithm to build block sequences, the ARQ feedback intensity, a scheduling of the ARQ feedbacks and retransmissions, the ARQ block rearrangement, ARQ transmission window and the ARQ block size. We ran simulation scenarios to study these parameters and how they impact the performance of application protoc…

Performance comparison of HARQ and ARQ mechanisms in IEEE 802.16 networks

The IEEE 802.16 technology defines several link level mechanisms to retransmit erroneous data. In this paper we compare the performance of the ARQ and HARQ mechanisms in the IEEE 802.16 networks. Our simulations results show that in general HARQ provides a better performance. However, ARQ can compete successfully with it due to a smaller signaling overhead. Furthermore, since ARQ does not require a dedicated uplink signaling channel for the acknowledgments messages, it results in better resources utilization in the uplink direction.

Impact of portable device restrictions on IEEE 802.16 performance

IEEE 802.16 is a good alternative for fast wireless connection in the next generation portable information devices (PID). However it was not originally designed for portable devices, but mobility was added later to the specification. This means that the lack of resources on portable devices might have a significant impact on which IEEE 802.16 features should be chosen and how they should be used. Proper usage of ARQ can increase the IEEE 802.16 performance but it can also require much resources from PIDs. In this paper we focus on how ARQ features are affected by limited resources on PID and how much the limitations affect on the performance.