Like 4G project, the MANET (Mobile Ad-hoc Network) is also in a developing stage. While defining the MANET standard, the Internet Engineering Task Force is working on routing techniques, like Ad-hoc On-Demand Distance Vector (AODV) defined in RFC 3561 [2] and Optimized Link State Routing Protocol (OLSR) defined in RFC 3626 [3], allowing self-configuring network of mobile nodes with routing capabilities [1]. MANET standardizes the static and mobile techniques of creating mesh networks using available wireless technology. Currently, 802.11a/b/g/n wireless networks defined by the IEEE standards are being used at homes, offices, and also could be found in the initial MANET infrastructure. Thus, what limits cellular networks and WLANs will limit MANET as well. On the other hand, any solution that can increase capabilities of wireless networks can influence capabilities of MANET as well and furthermore could mitigate serious issues like hidden terminal problem and fading.
New wireless communication technologies are expected to significantly influence the design and implementation of MANETs in the military environment. Since the future technology combining wireless local networks and cellular networks is more and more being referred to, and defined as the fourth generation (4G) of communication systems, it is critical to understand the meaning of 4G and its potential in influencing wireless networks, particularly MANET. Since we should assume low infrastructure of the mobile ad-hoc networks in the hostile military environment, 4G could be an answer to offer significant solutions for mobile MANETs to achieve high quality transmissions and constant connectivity. However, the implementation of 4G may be significantly more complicated than in the civil environment due to the unique specification and requirement of the military environment. We introduce the term 4GM@4GW that describes possible issues of the forth generation of cellular network implementation in the forth generation of warfare.
This paper is organized in the following way: Section 1 introduces the paper. Section 2 presents different perspectives of the 4G design. The most probable design and capabilities of the 4G are presented in Section 3. The following sections describe the definition of 4G as a significant factor influencing wireless networks. Section 4 details how 4G technology might influence networks. Section 5 highlights implementation issues of 4G in the mobile military environment by introducing 4GM@4GW terminology. Finally, Section 7 concludes and describes future work.
4G stands for the fourth-generation cellular network. Although it is generally agreed that 4G is going to offer better communication technology than 3G, it is still undefined as to which areas should be really improved upon, and in which ways, from 3G. Researchers are often pointing towards integration whereas business institutions are working on upcoming technologies that will make 4G more attractive to the business community by implementing it more customer-friendly. This section presents different perspectives on how 4G is defined. Later, we will investigate how the forth generation of mobile wireless networks (4GM) can be implemented in the modern military environment known as the forth generation on warfare (4GW). We introduce term 4GM@4GW to discuss issues of implementing presented technology in the military mobile environment.
New support for mobility is the primary concern of Hussian et. al. and they pointed out insufficient 3G mobility constrained by bandwidth that should be significantly increased. According to them, the significant progress that 4G can achieve in the area of mobility is unifying different and currently separated environments into a single fixed OWA (Open Wireless Architecture) that will achieve high connectivity by accessing all kinds of networks. Invented by the Delson Group's R&D division, OWA is a project working on developing a unified global standard of mobile communications to achieve global mobile access, high quality of service, with a single fundamental component allowing easy transmission of all kinds of data . Providing single terminal that will effectively access the best available internet connection will increase and speed up device usability under 4G.
Integration is the key concept in defining 4G capabilities since we should support all kinds of multimedia by offering single access to all wireless networks. Understanding the significance of unifying Wi-Fi, WiMax and Cellular networks into one product, Woerner and Howlader proposed that the most important factor of 4G will be "seamless integration of wireless networks" based on flexibility of the software radio technology, with improved bandwidth capacity, and improved routing techniques allowing multi-hop peer-to-peer networks. Due to the lack of single military scenario where and how 4G will be used, it is critical that future wireless technology will be capable of effortlessly accessing all kind of radio communications.
Bauer et. al. addressed that enhanced cellular range and capacity, supported by Wi-Fi and WiMAX networks is the vision of 4G . However, considering the fast development of WiMAX networks, and the increasing range of Wi-Fi standards, they argue that these new wireless networks can in the future substitute cellular networks such as the current 3G. They also addressed that it is "misleading" calling the evolution of cellular technology in terms of generations because this would "suggest a linear progression" which is not the case. Finally, they also evaluated business opportunities of 4G pointing out on establishing a global standard, along with open architecture, and supporting multiple interfaces all over the world, as the keys to economical success.
DVB (Digital Video Broadcasting) is the "global standard for the global delivery of digital television and data services ." Researchers see DVB-H (Digital Video Broadcasting - Handheld) and DMB (Digital Multimedia Broadcasting) as additional component of 4G providing video transmission to mobile devices. Understanding technical requirements of soldiers fighting on the battlefield, we believe that DVB can become a significant utility for army by providing necessary information such as soldiers' view and access to maps and immediate satellite pictures.
The general concepts of 4G can be present in the list as follows:
Improved capacity
Increased number of users in the cell
Lower transmission costs
Connection with already existing systems
Lower latency
Based on ipv6 protocol, with packet switching
Single interface for all wireless connections
Increased mobility
Support for media applications
Seamless connectivity
Improved security
Improved and guaranteed quality-of-service
Global roaming of networks
Standardized open interface
Self-organizing networks
Fast response
3. 4G - The Final Definition
There are two paths leading toward each other whose goal is 4G. One path defines the evolution of 3G cellular systems into more advanced 4G technology that will recognize and be supported by Wi-Fi standards and upcoming wireless networks technologies. The other path successfully deploys high bandwidth and introduces highspeed mobility emerging from currently popular Wi-Fi technology and upcoming standards such as WiMax 802.16 supported by mobility amendment 802.16e and additional projects like 802.20 considering mobile broadband wireless networks. For the second group of people leading toward 4G, cellular networks are additional supporting component offering complete integrity with all available wireless connections.
Steer addressed 4G is officially designated by IEEE as "Beyond 3G." Characterized by wireless broadband with over 100Mbps mobile capacity and 1Gbps stationary bandwidth supported by OFDM, MIMO, and software defined radio, Steer presents new 3G's components that will upgrade it up to 4G. The idea of upgrading 4G is shared by two other groups working on the next generation technology 3GPP and 3GPP2 developing new versions of UMTS and CDMA2000 cellular systems respectively.
Fig. 2 Evolution of 4G
After introducing HSDPA (High-Speed Downlink Packet Access) in release 5, HSUPA (High-Speed Uplink Packet Access) in release 6, and HSOPA (High Speed OFDM Packet Access) in release 7, the 3GPP group project is working on release 8 — the UMTS (Universal Mobile Telecommunications System) Revision 8 LTE (Long Term Evolution) that will introduce 4G on UMTS foundations . The 3GPP plans presented in Technical Report (TR) 25.913 that are going to be concluded in September 2007 expects cell coverage between 5 to 30 km, latency below 100ms, 100 Mbps/50Mbps downlink/uplink data rate within 20MHz spectrum allocation, high performance mobility up to 120km/h that between networks can be increased as much as up to 500km/h. The same report signifies the importance of IP-based networks with support of MIMO and OFDMA. Currently Ericsson's antennas allow 144Mbps transmission .
Based on IS-95 (Interim Standard 95), CDMA2000 is third generation telecommunication standard that became foundation for 3GPP2 (Third Generation Partnership Project 2) project introducing 4G known as UMB (Ultra Mobile Broadband). Like UMTS 8 LTE, UMB will be supported by MIMO and OFDMA. With full mobility, UMB offers over 100 Mbps transfer using beam-forming signal processing technique from smart antennas , which although highly complex and still significantly costly after integration with MIMO allow high data rates particularly in scattered environment
Whereas 3GPP and 3GPP2 are upgrading 3G technology up to 4G, the groups like the WiMAX Forum are developing solutions that increase capabilities of wireless local networks. An organization of over 400 leading operators called WiMAX Forum is working on technology offering wireless alternative to DSL and cable providers based on IEEE 802.16 and HiperMAN standards called WiMAX (Worldwide Interoperability for Microwave Access ) . While stationary, within the cell radius of 10 km, WiMAX Forum Certified™ systems allows 40Mbps transfer, and 15Mbps transfer, in 3km radius, while mobile, using OFDMA and advanced antenna techniques with MIMO. The bandwidth capacity can be increased by lowering the range, and vice versa.
WiBro (Wireless Broadband) is the Korean alternative to WiMAX. Offering mobility of up to 60 km/h, with service coverage up to 1 km, handoff less than 150 ms, maximum download 3 Mbps and maximum upload 1Mbps, WiBro is an important support to mobile wireless research projects . Cooperating together, IEEE 802.16, WiBro, and HIPERMAN, will create single version of WiMAX based on American, Korean, and European developments of broadband mobile wireless networks.
Considering mobility of future 4G technology, two additional working groups IEEE 802.16e (Mobile WiMAX), which is the amendment to IEEE 802.16a, and IEEE 802.20 (Mobile Broadband Wireless Access) provide new wireless broadband services. Although similar because both goal at low latency on packet architecture with at least 1 Mbps transfer , 802.16e and 802.20 target on different speeds of nodes. The 'e' amendment maintains the 802.16 achievements adding vehicular mobility . The networks' access from trains traveling with speeds up to 250 km/h will be possible using mobile broadband wireless access defined by IEEE 802.20 .
Looking back on different paths leading toward next generation communication system, 4G emerges as a puzzle of many components that when connected together properly, complement each other's technological holes such as mobility, range, or bandwidth creating the 4G picture that provides global, single, and a simple standardized way of accessing it such as puzzles have one, by everybody known, way of putting them together. The Pioneer and Inventor of 3G/WiFi Convergence Systems and Technologies, Top Global USA, Inc. created the first such 4G picture, the first mobile router that links 3G/4G Cellular and Wi-Fi networks. Providing seamless routing and secure connectivity, Top Global's router maintains connection in moving vehicles with 802.1 1n, HSDPA, and WiMAX wireless access points simultaneously .
In this section, we observed how 4G technology will simplify implementation of wireless networks and at the same time increase mobility, bandwidth and range on the radio signal in the civil environment. As we will investigate in the later sections, it might be more difficult to achieve same successful results from 4G in the military environment compared to the civil environment in a metropolitan area. already accepted by researchers as one of the main components of projects such as WiBro, WiMAX, WLAN, 802.1 1n, UMTS R8 LTE, and UMB.
Fig. 3 4G mobility, bandwidth and range in military environment4. Networks with 4G
Although there are different ideas leading toward 4G, some concept and network components frequently come up as a supporting and significant solutions that help achieve progress toward 4G. In this section we are going to investigate and explain technological innovations such as MIMO (Multiple-Input Multiple-Output), OFDMA (Orthogonal Frequency Division Multiple Access) and HIP (Host Id Protocol) that could significantly increase security, mobility and throughput of 4G.4.1 MIMO
Imagine that you can hear better what you want to listen, and don't hear what bothers you, just by pointing out where message and noise are coming from. Beamforming that is the significant concept of MIMO (Multiple-Input Multiple-Output) allows you do just that using smart antennas system. But that's not all what MIMO has to offer. Spatial multiplexing, achieved by independent simultaneously working antennas, increases bandwidth capacity by modulating and transmitting signal through many paths . Using space-time coding, reliability is improved. MIMO achieves great success thanks to multiple antennas that allows simultaneous directional transmission of two or more unique data streams sharing the same channel. Increasing speed and range, MIMO is
Datacomm Research Company proposed the simplest way to implement MIMO is by sharing frequency using OFDM, that together significantly can increase performance by extending range, boosting speed and improving reliability. Together with MIMO, OFDMA is another component of 4G that as the alternative to CDMA, promises high data capacity and spectral efficiency. OFDM (Orthogonal Frequency -Division Multiplexing) is the modulation scheme which divides allocated frequency channel into many narrowbands guaranteeing mutual independency between subcarriers such that there is no interference between them; signals are orthogonal .
Before OFDM become popular, three other solutions were presented to share radio spectrum between multiple users. Used by 1G, FDMA (Frequency Division Multiple Access, Fig. 5) partitioned channel between users. To increase channel capacity, TDMA (Time Division Multiple Access, Fig. 6) was proposed that allocate each user access to the whole bandwidth for short period of time.
Fig. 5 FDMA
Fig 6 TDMA
Because TDMA in 2G caused interference problem, CDMA (Code Division Multiple Access) was proposed as a new form of multiplexing where each user was allowed to use the whole channel capacity all the time. Different messages were transmitted with associated special code which was later used to distinguish between them.
Fig. 7 CDMA
The better data throughput become possible, when using orthogonal frequency division multiplexing, the radio bandwidth could be subdivided into narrowbands.
Ø Distribution by fixed frequency
Ø Randomly hopped subcarriers
Ø Distribution using tdma
Ø By spreading subcarriers in a comb pattern
Ø By adaptive user allocation
The simplest method of sharing performance achieved by OFDM is distribution using TDMA known as OFDM-TDMA . OFDM-TDMA can be represented by Figure 6, considering that frequency channels are orthogonally subdivided as in Figure 9.
Fig. 9 Sharing frequency in OFDMA
4.2. HIP
Fig. 11. When moving from one network to another, host id stays same and IP address changes.To simplify nodes mobility, HIP (Host Identity Protocol) was proposed that would introduce additional Host ID layer between transport and network layer to the internet protocol stack (Figure 10) and enable continuity of communication by establishing connections with host ids, but not with host locations. Host identifiers are 128-bit public keys, called Host Identity Tags (HIT), for which hash function is applied [29][30].
Fig. 11. New Host ID layer will simplify nodes' mobility in 4G.HIP will not only enable end-host mobility, but will also simplify multi-address multi-homing with integrated security over IPv4 and IPv6 . Although the multi-homing features are already available through SCTP (Stream Control Transmission Protocol) that was designed to provide better transmission service for multimedia applications such as video-streaming and VOIP and supports packet delivery using multiple streams , none of the popular internet application are using SCTP yet because of its complication in use. The end-point identifiers called host IDs are public keys. Whenever a client request a connection with a host address, DNS returns a Host ID, that later is translated to an IP address. Thus end-point identifiers are controlled by Host ID layer, and host location is controlled and properly updated by the network layer . Finally, HIP has another benefit of its resistance to CPU and memory Denial-of-Service attacks as well as the Man-in-the-Middle attack. Encapsulated Security Payload and available encryption for TCP and UDP also signifies the security importance of HIP . The HIP project of IETF will be scheduled to be finished by end of 2007.
From earlier sections, we investigated many faces of the forth generation of cellular network. Its final definition as well as main concepts influencing the progress of wireless network technology toward 4G portrays the future society living in utopia of constant access to all kinds of information through wireless communication. Someone may think that such technology is already accessible while walking on the streets of New York. New Yorkers, with all kinds of technical equipments that they are carrying, such as cell phones, PDAs, and laptops, are able to access information through cellular networks or local wireless networks from the free public hotspots installed by NYCWireless community or networks in homes, offices, or restaurants and bars. New York needs single terminal allowing access to all kinds of wireless technologies and business support that will take a profit, to step up into 4G. However, unlike commercial environment, 4G implementation and secure constant connectivity may require tremendous work in a military environment.
The next generation of wireless technology requires understanding the future of warfare: the 4GW. 4GM@4GW is the idea of implementing the forth generation of wireless technology into mobile ad-hoc network in the next generation military environment. To understand this concept better, we will fist explain the 4GW term defined by William Lind, an American expert on military affairs, as the theory of the Forth Generation War.
Lind addressed the history of warfare can be divided into four generations. The first generation of warfare is characterized by significance of man power; the winner had simply more soldiers. The second generation focused on firepower. During World War I, armies were staying on the line, shooting toward each other, and the winner was the one who could survive the hell by having access to more artillery. Focusing on speed and coordination, the idea of highly mobile military introduced by the Nazi Germany during World War II as flash war (ger. Blitzkrieg), illustrate the third generation where "attack relied on infiltration to bypass and collapse the enemy's combat forces rather than seeking to close with and destroy them" . The news coming from Iraq and Afghanistan show examples of the forth generation of warfare known as 4GW, which is characterized by vanishing line between peace and war, and no existence of battle front . According to [27], the 4GW "includes all forms of conflict where the other side refuses to stand up and fight fair."
Fig. 12 Hidden terminal problem: soldiers signal are prevented from hearing each other. The signal to the destination car is interfered.
4GM@4GW will be supported by 4G using increased mobility, range and bandwidth, single terminal connectivity with all already existing military equipment, possibility of using any present technology maintaining communications on the territory of action, and supported by MANET's mobile mesh routing in case of lack infrastructure. At the same time, 4G(M@W) will be twisted by technical limitations, natural-geographical constraints, possible breakings of encryption code, and DoS (Denial of Service) attacks.
Technological limitations defined as physical constraints in terms of bandwidth, memory, and power, are the first significant point on the list of issues in 4GM@4GW. This paper defines the possibilities of increasing bandwidth using the forth generation of wireless communication. Currently accessible on market different kinds of memory allow us to assume that sufficient and low cost memories, such as flash drives, should fit into military environment. However, the important issue arises from supplying military mobile electronic devices by sufficient amount of power that is dependent on: how 4G is going to be implemented, what routing protocol will be applied, in what urban-geographical environment missions will take a place, and finally the duration of missions.
Fig. 13 Enemy forces use jammer to interfere army's signal.Comparing to the implementation of 4G in the civil environment, 4GM@4GW is also constrained by enemy's action preventing successful communities of army forces and technological devices left on the battle field by enemies for the purpose of disrupting the wireless communication. Such an activity does not have to focus on decrypting information that is sent through air, but simply on preventing information to reach the soldiers by using DoS attacks (Figure 13). In many cases, successful DoS can be more important that decrypting information because of its immediate influence on the army's condition.
The era of new wireless communications is upon us. Eventually it will be penetrated into our daily life just like many technological breakthroughs whose original research came from the military needs. Automatic high-way traffic control system where vehicle equipped with sophisticated embedded communication chips can enter and leave from the infrastructure dynamically will be one example among many potential applications from 4G and MANET combined scenario.
The future work includes: define physical constraints for military mobile devices, simulate the effectiveness of MANET's routing protocols in 4G environment to find the most optimal protocol for the 4GM@4GW.
