HFLINK Comments to ARRL
on Development of
New HF Digital Communications Protocols
An international resource for radio operators for
ALE Automatic Link Establishment,
High Speed and Robust HF Digital Communications,
and Ionospheric Propagation.
Attn: Paul Rinaldo, Chief Technology Officer
Re: HFLINK Comments to ARRL on Development of New Digital Communications Protocols
Date: 14 May 2007
On 22 Feb 2007, the ARRL announced See Note 1 that it seeks comments from amateurs concerning development of an open-source, non-proprietary, data communications protocol suitable for use by radio amateurs over HF fading paths.
HFLINK, an international resource for radio operators, for High Speed and Robust HF Digital Communications, ALE Automatic Link Establishment, and Ionospheric Propagation, with a membership of 1200 radio operators, including more than 900 licensed operators in the amateur radio service of USA, discussed ARRL’s announcement at length in the HFLINK Forum and via private correspondence.
HFLINK now respectfully submits the following comments in response to ARRL’s announcement:
We don't believe it is necessary to re-invent the HF data wheel for digital communications protocol, or desirable to invent a completely new ham-only standard digital data protocol built from the ground up, especially when we can leverage a suite of existing USA and global HF standards to provide an excellent working protocol for the ham community. Any modulation or coding system proposed should be intellectual property rights free, either by being in the public domain, or by having any patent holders issue a free non-discriminatory license for non-commercial use. Another consideration is that the protocols should bear in mind that such common standards last for decades, and thus should not be tied or limited to today's hardware capability or a unique platform, bandwidth, or present regulatory symbol rate limit. We believe that existing FED, MIL, and STANAG HF data communications standards provide a wonderful basis for expansion and development in amateur radio service. We can leverage and be the beneficiary to the vast research and development that has been expended.
In this document, we offer the following recommendations and research to support our comments:
PSK and MFSK for Data Communications
Recent advanced research and development in the HF industry arena for commercial and governmental applications has shown that PSK and MFSK with single tone physical layers tend to excel in the area of ARQ data HF communications. While OFDM based physical layers with FEC tend to excel in the area of HF Digital Voice applications. With regard to PSK and MFSK, the power levels of the transmitted signal are at nearly constant high amplitude, and the nature of the signal at high speeds does not require the kind of careful transmitter adjustments, high specifications, and linearities that OFDM with amplitude modulation needs for maximum throughput and signal integrity. Therefore, since this comment document is in response to ARRL’s desire for responses concerning data communications protocols, we hereunder recommend the adoption of PSK and MFSK based physical layers for data communication, especially for ARQ data. Since amateur radio equipment of all types will be used by operators, it is important that the physical layer of the data formats be robust and clean with little need for special ALC constraints or stringent IM3 specifications. Slower TR switching is also a requirement if existing ham radio equipment and PC computers are to be enabled by the adopted protocol standards when using ARQ. Successful systems meeting these constraints have been demonstrated, and indeed are already in use by ham operators in USA and internationally.
Digital Voice OFDM and HF Digital Voice Repeater
As an auxiliary comment, we recommend more research and development of OFDM physical layers for digital voice, specifically in the area of a scalable physical layer protocol, able to be time-multiplexed and interleaved, using bursts of compressed voice data, to enable a single-channel digital voice repeater on HF in a 5kHz or 6kHz bandwidth. The application of such a digital voice repeater, with less than 2 seconds realtime delay, on HF in emergency and relief applications is tremendous. The potential for day-to-day popularity of such a system would ensure its ready use, and also extend the amateur radio community in a forefront position for HF technology.
Existing Standards, Especially STANAG 5066, Ready for Further Amateur Development
MIL-STD 188-141, MIL-STD 188-110, FS-1045, FS-1052, and STANAG 5066 standards are ready for hams to use for the purpose of HF digital communications. Existing software and hardware solutions presently exist, and are in use by hams, for most of these protocols. We especially see the 5066 protocol as a wonderful area of data protocol where ARRL could benefit the entire amateur radio community by encouraging and fostering development of a PC-based program. 5066 is a modem-neutral protocol layer that provides a non-proprietary system for HF data communications interface with internet protocols. It is presently in use by governmental and non-governmental entities on HF, as a workhorse for HF digital data communications including HF email and other HFIP applications.
Recommending Adoption of a Protocol Suite
In the following comments, HFLINK proposes the adoption of several existing data protocols for different purposes of data communications, along with some new protocol development, forming a suite of protocols as a standard. ARRL is in a good position to develop and adopt such a standard, and for that standard to be used throughout the international ham community. HFLINK especially sees the advantages of such development for application by amateur radio service in Emergency and Disaster Relief. In order for the ham community to establish readiness in this area, it is necessary for hams who use the protocol and standards to have good familiarity and daily operations communicating via the standards. It is only with common use of these communications that emergency capability will be ensured. Thus, the standard should provide day-to-day utility that serves the needs of hams for common texting, calling, email, SMS, and data messaging. The various levels of protocol recommendations are described below, and detailed in Tables 1, 2, 3, 4, 5, 6, of this document.
Foundation of Protocol Suite: Physical Access
We propose that new HF digital standard protocols be based upon a foundation of Automatic Link Establishment (commonly known as 141 ALE) for access at the primary connection level between station-to-station and station-to-server, and that a multi-tiered approach to protocol standard levels and data transfer methods be used to accommodate existing equipment and anticipate future needs and development.
The use of 141 ALE at the foundational Access Protocol Level provides an existing system with a proven track record, that bridges all operating systems and platforms. It is currently available embedded in HF transceivers. 141 ALE is presently in use in the amateur radio community, and successful implementation of ham radio friendly ALE standards of operation, forged and developed by HFLINK over the past 6 years, has enabled 141 ALE to exist without interference problems. This includes the international coordination of HF channel frequencies, the use of polite and busy-channel recognition procedures, and the use of ALE protocol settings that are optimized for ham radio. ALE was originally envisioned as a way for unskilled operators to establish communications on HF. The amateur radio community has adopted and molded ALE into something more than the originators had envisioned. In the hands of a skilled amateur radio operator, ALE is a wonderful tool for communicating. It enables the unparalleled excellence in use and discovery of HF ionospheric band openings, the ease of selective calling of stations, the calling-up of hot-standby nets, instant CQ answers, bulletin dissemination, along with brief text messaging as an added bonus. It also includes the use of busy-channel detection, and fluid SSB voice in various embodiments.
Proposed ALE Station Installation at W1AW
We propose that ARRL set an encouraging example for the ham community by installing a 141 ALE HF station at W1AW and immediately begin transmitting QST announcement bulletins using ALLCALL address ALE on the internationally recognized amateur radio ALE data and voice channels. The proposed format for QST announcement data bulletins using 141 ALE is initial AMD header, followed by 141 ALE -based 8FSK using non-ARQ DBM. Such a 141 ALE station at W1AW is a perfect flagship platform for implementation of the communication protocol standards developed by ARRL through this comment process.
141 ALE is completely OS neutral. It is a US
federal standard, published and free for hams to use worldwide. Over the past 5
years, 141 ALE has become the defacto universal global standard
for HF connectivity for voice and/or data communications. Until recently, only
about a thousand hams had 141 ALE capability, using commercial ALE transceivers
and ALE controllers or PCALE software with amateur transceivers. In 2006, two
new embedded HF ALE transceivers became available on the market in the amateur
radio price range (under $US1500), the Icom IC-F7000, and the Vertex VX-1700
(Yaesu). In 2007, MULTIPSK software added 141 ALE with ARQ data. HFLINK is
presently corresponding with other ham software authors who are working to add
141 ALE in their products. The addition of 141 ALE into the popular MULTIPSK
software has greatly expanded 141 ALE among thousands of hams worldwide,
Some advantages of 141 ALE for amateur radio use:
ACCESS INITIAL PROTOCOL LEVEL See TABLE 1
We recommend adoption of protocol MIL STD 188-141, FED-1045 for calling, Automatic Link Establishment, alerting, connecting, CQ, QSY, interoperability, and net management.
We recommend adoption of protocol MIL STD 188-141, FED-1045 for short text messaging, bulletin transmissions, QSTs, SMS-messaging, short email text messaging, and interoperable messaging.
We recommend adoption of 8FSK ARQ, derived from MIL STD 188-141, FED-1045, for medium speed text-based and binary-based messaging, email, keyboarding chat, etc.
We recommend adoption of PSK - ARQ, derived from MIL STD 188-110, using a modified physical layer 6PSK at 2400 baud ARQ and non-ARQ, and the 110 standard 8PSK up to 4800 baud ARQ and non-ARQ, for high speed email, chat, chatroom, mobile web browser, internet functions, etc. These formats are presently available in the PCALE, MARS-ALE, and RFSM-2400 software modems, and usable with amateur equipment. They provide impressive throughput and robustness.
DATA ADVANCED PROTOCOL LEVEL 2 See TABLE 5
We recommend the new development and adoption of existing higher speed PSK with FEC and ARQ for high speed email, digital voice, mobile web browser, internet functions, etc. ARQ functions should be compatible with slow TR switching.
DATA HF-IP PROTOCOL LEVEL See TABLE 6
We recommend the adoption of Stanag 5066 (Open 5066) and FS-1052 in the interim, for higher protocol layers, for interface with the internet, management of data traffic, and interface between networks. We recommend that ARRL fosters and encourages development of 5066, and commences a project to develop a 5066 software program for PC, and use it as an open standard protocol for the Amateur Radio Service for HF internet.
If a development path for new physical and protocol layers is embarked upon, it is suggested that it includes the following:
1)The ability to rapidly detect the presence of the waveform on channel even if off tune for CSMA (busy-channel detection) purposes.
2) Scaleable to different channel bandwidths
3) Support ARQ and Broadcast.
4) Bitpipe including a sync on data capability
5) Packet mode
6) Open source
7) Channel Adaptive
8) Tolerant of transmitter misalignment
9) Ability to track Doppler shift and transmitter drift
10) Ability to tolerate Doppler spreading
11) Can be used on VHF as well as HF
12) Support for digital voice
HFLINK respectfully asks ARRL to carefully consider the comments and recommendations provided in this document. We believe ARRL is in a unique position to encourage and foster development of standards in the amateur radio service of USA and the ham community worldwide.
Submitted on behalf of the members of HFLINK Forum and HFLINK,
Bonnie Crystal, KQ6XA
ATTACHED NOTES AND TABLES
TABLE 1 - INITIAL ACCESS LEVEL
TABLE 5 - DATA ADVANCED LEVEL 2
TABLE 6 - DATA HF-IP LEVEL
NOTE 1 - ARRL Seeks Comments on New HF Digital Protocol
END OF DOCUMENT