The new technique: FLASH-OFDM

Hi,
Can someone explain the new technique FlASH-OFDM.
How this technique differ from OFDM,? What are the advantages ?
I have tried to get some papers on FLASH-OFDM but with no success.
If someone can upload a paper i would be very grateful.
Thank you.

Re: FLASH-OFDM

Bumbar,

**broken link removed**

Wired IP communication systems employ a "layered" network protocol design, made up of 5 layers that perform certain functions in the network. The physical, medium access control (MAC)/link and network layers are responsible for network access. FLASH-OFDM takes the same approach and applies it to a wireless medium.

The physical layer, also known as the "pipe," deals with the physical means of sending data over a communications medium. The MAC layer controls access to that "pipe" and shares it among many users, while the link layer uses procedures and protocols to carry data across it (the link layer also detects and corrects transmission errors). Finally, the network layer is responsible for routing within the wireless network, as well as for determining how data packets are transferred between modems.

FLASH-OFDM is a vertically integrated design spanning the physical, MAC, and link layers, while the network layer and the remaining layers are horizontally layered, inter-networked and purely IP-based, enabling reuse of existing off-the-shelf IP infrastructure equipment and protocols. This all-IP infrastructure is one of many reasons why FLASH-OFDM is able to deliver a user experience that mirrors a wired broadband connection.

FLASH-OFDM Physical Layer
The OFDM physical layer creates a robust multiple access technology to deal with the impairments and uncertainties of the wireless channel. FLASH-OFDM goes further, dividing the available radio spectrum into a number of equally spaced and orthogonal tones and using fast frequency hopping across those tones to become a spread spectrum cellular technology. Spread spectrum allows the data to be packetized and spread out over a wide range of bandwidth, then re-assembled into its original message. Because of this, FLASH-OFDM supports a larger number of users and transmissions, and is highly secure.

Because of its spread-spectrum design and the orthogonality of its tones, FLASH-OFDM captures the significant advantages of CDMA (frequency diversity and intercell interference averaging) and TDMA (intracell interference averaging). In addition, because of its resource allocation attributes, the FLASH-OFDM physical layer makes it possible to transmit a single bit with essentially no overhead. This efficiency, not seen with circuit-switched technologies, dramatically reduces overall complexity, costs and latency, and enables the development of a very fine-grained and flexible MAC/link layer.

FLASH-OFDM MAC/Link Layer
The responsibility of the MAC and link layers is to efficiently and reliably share the physical layer ("pipe") among a large number of mobile users. While the capacity and efficiency advantages of the FLASH-OFDM physical Layer are significant, it is the MAC and link layers where even larger differentiators are found, including contention-free access for low latency and enhanced Quality of Service (QoS), fast automatic repeat request (ARQ) for low latency and greater reliability, and session control for bandwidth maximization and overall user capacity.

The FLASH-OFDM MAC layer leverages the ability of OFDM to support many low-bit-rate dedicated control channels (those that carry very little data), enabling a larger set of active users and traffic streams. FLASH-OFDM IP awareness provides the ability to distinguish between the priorities of each user's traffic and application services (packets flows are classified with fine granularity), allowing wireless operators to maximize revenue through multi-tiered pricing; public safety agencies and enterprises to have priority access over less critical users; and end users to choose service plans based on their needs and budgets. Contention-free access in FLASH-OFDM also reduces overall latency, making the experience similar to wired broadband systems.

One of the more important aspects of the FLASH-OFDM MAC layer is its ability to rapidly schedule active users between 'on state' (users are downloading a web page) and 'hold state' (users are reading that web page). Sharing the pipe in real time among only those users who require it results in efficient use of bandwidth, low overall latency and enhanced QoS for a large number of mobile users. Enhanced QoS enables mobile operators to maximize revenue through tiered services, and the public safety and security sector to have priority access over less critical users.

The link layer runs over and uses the physical layer to carry data from a transmitter to a receiver, and is responsible for network reliability. FLASH-OFDM provides high reliability through a link layer that features a fast automatic repeat request (ARQ), which is used to check transmitted data for errors. If one is found, the message is retransmitted very quickly. Therefore, with loop times at less than 10 milliseconds, FLASH-OFDM ARQ latency is very low. This enables low-latency retransmission of frames received in error, and allows end users to run applications as they would on their wired broadband connection.

This combination of high reliability and low latency is critical for support of interactive applications, such as voice over Internet protocol (VoIP), instant voice and data messaging, online gaming and a host of other enterprise-specific applications. It also equates to overall performance. FLASH-OFDM downlink typical data rates of 1 to 1.5 Mbps are exactly that, because the system quickly repairs transmission errors so that data flows without interruption.

FLASH-OFDM Network Layer
FLASH-OFDM was designed to be seamlessly deployable within a pure IP-based network architecture and complies with the IETF architecture. As such, the technology uses IP mobility management, IP security and IP QoS, while removing the need for specialized radio access networks and complex/costly protocols.

The RadioRouter® base station is a combination of a wireless base station and an IP access router that performs in some ways similar to an IP-savvy WLAN access point, but provides fully mobile, wide area network coverage. All network access functionality resides in the RadioRouter base station, which wirelessly extends the edge of the IP network.

The autonomy of the RadioRouter base stations is one of the more critical attributes of the FLASH-OFDM network layer. In adjacent cells, RadioRouter base stations do not need to be aware of each other, and timing or frequency synchronization is not required between them. These characteristics translate into lower system planning, deployment and maintenance costs, which allow administrators to deploy a cellular infrastructure more similar to that of a wireless LAN.

This autonomy leads to another advantage at the network layer - RadioRouter base stations are backhaul-agnostic, meaning that they can attach to an IP domain via any backhaul technology (T1, gigabit Ethernet, ATM, etc.). This leads to a very scalable and flexible architecture, which permits the IP domain to use any IP networking infrastructure to lower costs.

Hope this helps,
mindrover