Special Feature

Functions of PC Communicator: PC-toFOMA IP Videophone Technology
Hideaki Takeda†, Dai Ando, Sumitaka Sakauchi,
Shigehiko Onishi, and Hirohisa Jozawa
Abstract
This article describes the point-to-point communication functions of the “PC Communicator” Internet
protocol (IP) videophone/videoconferencing system developed by NTT Cyber Solutions Laboratories.
The PC Communicator provides voice-over-IP telephony between a personal computer (PC) and various
types of terminals such as another PC, PSTN (public switched telephone network) phone, cellular phone,or PHS (personal handy-phone system) phone. It also provides IP videophone connections between a PC
and a FOMA or “.Phone Personal V” phone from NTT DoCoMo and NTT Communications, respectively.

1. PC communicator
NTT Laboratories and NTT Resonant Inc. havedeveloped the PC Communicator (PCC), an Internet
videophone/videoconferencing system that conforms
to SIP*1 (session initiation protocol). PCC is the NTT
Group’s first wholesale type service*2. It is being provided to NTT Communications Corp. by NTT Resonant Inc. as “.Phone Business V” [1]. Commercial
services began in March of this year and wereupgraded at the end of May.
PCC handles both point-to-point and multipoint
calls among personal computers (PCs) and phone terminals, both fixed-line and mobile ones. A detailed
explanation of multipoint calls is given in the third
article in this Special Feature “Videoconferencing
Technology for High-quality PC Multipoint Connections” [2]. Here, we explain the point-to-point communication functions of the PCC.
2. PCC system configuration
PCC is integrated with a video communication service to form the PCC system. This comprises several† NTT Cyber Solutions Laboratories
Yokosuka-shi, 239-0847, Japan
E-mail: takeda.hideaki@lab.ntt.co.jp

18servers, a FOMA network gateway (FOMA-GW), apublic switched telephone network gateway (PSTNGW), and client software that runs on a Windows personal computer (Fig. 1). The servers include a SIP
server that administers SIP call control, a presence
server that provides a presence service that indicates
whether or not a user is online and other such user
information, an instant messaging service, and a multipoint videoconferencing server that provides avideoconferencing service. The SIP server (calledType1-CA(SS)), presence server (called Type1CA(PS)), and PSTN-GW were developed by NTTNetwork Service Systems Laboratories. The network
technology that supports the PCC is explained indetail in the fourth article in this Special Feature“Network Technology to Support PC Communication Services” [3].
3. PCC functions
The functions of PCC are listed in Table 1. This

*1 SIP: An IETF (internet engineering task force) standard protocol
for establishing sessions for telephony, chatting, etc. between terminals on an IP network.
*2 Wholesale service: A form of service in which a company uses theservices and facilities of a service wholesaler to provide servicesto others.

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Special Feature

Network of company receiving the wholesaleservice (NTT Communications)

Network of company providing the wholesale service(NTT Resonant)Multipoint
videoconference server
Presence
serverPresence
server

PSTN-GW

SIP
server

SIP
serverIWEFOMA-GW

FOMAnetwork
FOMAterminal

PDC network

SIP hardware phone(OCN .Phone, etc.)

PCC client(.Phone Business V client)
SIP software phone(.Phone Personal,.Phone Personal V client)

PSTN network
PDC terminalInternationaltelephone
network

PHSnetwork

PHS terminal

Subscriber telephone

PDC: personal digital cellular phone

Fig. 1. PCC system and network configuration.
Table 1. Functions of PCC.

Point-to point
communication

Voice phone

Provides voice calls to analog phones, IP phones, cellular phones, etc.

Videophone

Provides video and voice communication between PCC terminals,
between PCC and .Phone Personal (V) terminals, and between PCC
and FOMA terminals

Instant messaging (IM)Provides point-to-point text-based conversation

Active member list (presence)

Displays log-in status (presence) and history

Address book

Stores addresses and other user information (calls can also be madefrom the address book)

Call history

Saves the history of incoming and outgoing telephone, videophone, IM,and videoconference calls (calls can also be initiated from the history)

Access control list

Assigns control of telephone and videophone calls and incoming instantmessages and presence queries

Whiteboard

Provides a point-to-point text and diagram sharing function

File transfer

Provides point-to-point file transfer

Videoconferencing
Multipoint
communication

Provides multipoint videoconferenceVideoconference chatEnables text messaging among participants

Videoconferencematerials sharing

Shares materials, whiteboards, and applications among videoconference
participants

section describes the main functions used in the
point-to-point communication.
(1) Voice phone function
The PCC client conforms to SIP and contains a SIP
stack*3 developed by NTT Network Service Systems
Laboratories. In addition, an audio echo and noise
Vol. 3 No. 10 Oct. 2005

canceller developed by NTT Cyber Space Laboratories reduces echoes and noise to ensure that the quality of voice calls is high.
*3 SIP stack: A software library that implements the SIP communication protocol.

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Special Feature

Table 2. Services compatible with PCC (.Phone Business V).
Service type

Connection type

Destination
OCN .Phone
OCN .Phone Office.Phone IP Centrex

IP-IP

OCN provider IP phone (050 number)(connection is free of charge).Phone Personal

Voice phone.Phone Personal V
Other provider’s IP phone (050 number)(connection is not free of charge)
Ordinary phone
Via PSTN-GW

Cellular phone (PDC, FOMA, and voice calls)
PHS
Ordinary telephone outside Japan (international call)Videophone

IP-IP
Via FOMA-GW.Phone Personal.Phone Personal V
FOMA

The SIP standard enables PCC to provide IP (Internet protocol) telephony between PCC clients and SIP
hardware/software phones connected to the SIP
servers of the company providing customers with thewholesale service (e.g., OCN .Phone or .Phone Personal) as well as between PCC clients (Fig. 1). The
PCC supports connections to both SIP hardware
phones (OCN .Phone, OCN .Phone Office, the IP
phones of OCN providers, etc.) and SIP software
phones (.Phone Personal and .Phone Personal V) registered in the SIP servers of NTT Communications.
Voice communication with analog phones, cellular
phones (PDC (personal digital cellular) or FOMA)and PHS terminals is also possible by connecting tothe PSTN via the PSTN-GW. The services that arecompatible with PCC are listed in Table 2.
(2) Videophone function
This function provides IP videophone communication between two PCC clients and between a PCC
client and a FOMA terminal. Video data is compressed and decompressed by an MPEG-4 codec
developed by NTT Cyber Space Laboratories toreduce the processing load while maintaining highvideo quality. Between PCC clients, communication
with screen sizes of CIF (352 pixels × 288 lines) or
QCIF (176 pixels × 144 lines) is possible. In addition,a function for VGA-size (640 pixels × 480 lines)
communication has also been implemented (but isnot provided for commercial use). During communication, the image size can be changed and communication can also be switched over to voice-only mode.
The videophone windows of the PCC are shown in20Fig. 2.
Video communication between PCC and FOMAterminals passes through the FOMA-GW. Smallscale FOMA-GWs for enterprises have been on themarket for some time, but large-scale systems forcommunication carriers have recently been introduced to produce the world’s first carrier service forvideophone connections between PC and cellular
phone terminals. The function for videophone connections with FOMA terminals, which is anothermajor feature of the PCC, is described in detail in thenext section.
The PCC client can make videophone connections
to both the .Phone Personal and .Phone Personal V
clients of NTT Communications. Because MPEG-4
encoding parameters are exchanged between thesending and receiving terminals in addition to the SIP
specifications, mutual MPEG-4 video connections
between different types of IP videophone terminals
are implemented through combination with theSDP *4 (session description protocol) description
specifications and interpretation method.
To exchange video codec information, SDP only
specifies the method for declaring the capabilities;
the operations at the receiving terminal side are notspecified at all. NTT Resonant Inc. has created common specifications for exchanging capability information for MPEG-4 connections between all the SIP*4 SDP: An IETF standard protocol for the exchange of session content information. It describes the types of video and voice codecs
and their parameters and is used for connection between terminals.

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Special Feature

Fig. 2. Example of videophone screen.

terminals offered by companies in the NTT Grouprather than just between the PCC client and .Phone
Personal V. We intend to work towards greater use of
the common specifications among all of the companies in the NTT Group.
(3) Active member list function
This function indicates the ‘presence’ of a person
registered in the active member list. That is, it indicates whether the person is online or offline, engaged
in a call, etc. (Fig. 3).
A member can use the access control list function
to specify whether or not his/her presence can beaccessed by others. If queries are blocked, no presence information is displayed. In addition to icons
that indicate presence status, this function allows text
messages to be entered in the presence field.
(4) Whiteboard function
This function enables text and diagrams to beshared with a specified party. It can display materials
prepared in advance and lets users write or draw on
top of them (Fig. 4). The user who initially activated
the whiteboard has control of the functions for creating, adding, or deleting shared screens (pages) andincorporating materials, but he/she can choose to passcontrol over to the other user. The shared screen canalso be saved as a bit map or in some other format.
The PCC whiteboard can also be used independently when communication with another terminal is not
Vol. 3 No. 10 Oct. 2005

PresenceOnline
Friends
MemberMy statusMessage
Office I’ll see you on videophone
Mr. Usami
Ms. OnoMr. Ikedo

Fig. 3. Screen showing the active member list.

taking place. The call connection is made using
SIP/SIMPLE*5 via the presence server.
(5) File transfer function
This function transfers files to a specified otherparty. In the same way as for the whiteboard function,*5 SIMPLE: An IETF standard protocol for the exchange of presence
and message information.

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MapHereFig. 4. Screen showing the whiteboard.

FOMA (3G-324M) terminal

FOMA-GW

PCC client

Display
Videocodec
MPEG-4Main data

System Multimedia
Resendcontrol signaling
control control
H.324
H.245

MUX/
DMUX

H.223

RTP

Video RTP
Sender/receiver

Video
codec
MPEG-4

RTP

Audio RTP
Sender/receiver

Audio
codec
G.711

IWE
converterFOMA
network

Display

CameraPRI

H.223

CameraSpeaker Audio
codec
Mic
AMR

Video RTP
Sender/receiverLinetermination

MUX/
DMUX

AMR⇔ Audio RTP
Sender/G.711
conversion receiver
H.245⇔
SDP
conversion

Call control
SIPdatacall control

Audio
capability
SIPSIP
Callcontrol

MicVideo
Speakers
capability

SDP
analysisH.324: ITU-T Recommendation. A multimedia communication system that uses the analog telephone network. 3G-324M is a specificationthat is based on the H.324 mobile network version H.324/M.
H.223: ITU-T Recommendation. A low bit rate multimedia multiplexing and demultiplexing protocol.
RTP: realtime transport protocol. An IETF standard protocol for realtime transfer of voice and video over a network.
H.245: ITU-T Recommendation. A procedure for performing format and protocol negotiation for calls between terminals.
AMR: advanced multirate codec. A voice compression and encoding method for flexible variation of transfer rate according to line type andconditions. It is used for third-generation cellular phones based on W-CDMA (wireless code division multiple access).
G.711: ITU-T Recommendation. The PCM (pulse code modulation) voice coding specification that is most widely used for IP phones.

Fig. 5. FOMA connection system configuration.

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Special Feature

Table 3. Functions of FOMA-GW.
Call processing conversion

H. 324 (Q. 931) ↔ SIP

Transport conversionH. 223 ↔ RTP

Media description conversion

H. 245 ↔SDP

Voice transcoding

AMR ↔ G. 711

Video transcoding

None (MPEG-4 through)Q.931: ITU-T Recommendation. A protocol for establishingconnections between terminals.

it can also be used independently, whether or not acall is in progress. The call connection is also madevia the presence server. It is possible to transfer files
directly (up to 100 Mbytes at a time) without an intermediate file server.
4. FOMA connection service(1) Connection method
The PCC uses Internet Protocol based on packet
switching which differs fundamentally from FOMA’s
64-kbit/s circuit switching, so a connection to eitherof them must go via a FOMA-GW. The system configuration for a FOMA connection is illustrated inFig. 5. The FOMA-GW is connected by a leased line
primary rate interface (PRI) to an NTT DoCoMo
IWE (interworking equipment). The FOMA-GW
converts between the specifications of the 3G-324M
and SIP IP phone standards. As shown in Table 3,
media description conversion for call processing conversion, transport conversion, and codec information
conversion between terminals and voice transcoding
are performed. The MPEG-4 codec of the PCC also
conforms to the FOMA specifications, so transcoding
at the FOMA-GW is not necessary. Thus, the processing load on the FOMA-GW is reduced and thechannel cost can also be reduced.
The screen size for a FOMA connection is QCIF,
which is the upper limit for the 3G-324M specifications. The specifications of the MPEG-4 encoder ofVol. 3 No. 10 Oct. 2005

FOMA terminals vary from manufacturer to manufacturer, but the PCC has demonstrated connectivity
with all devices of the FOMA 2102V series and later(900i, 901i, and 700i).
(2) Concept of use
Videophone connections between PC and FOMAterminals make possible ubiquitous video communication that is unrestricted in time or space. A few
examples of this are given below.
• Remote support and instruction from the officefor company employees who are out of the office.
• Remote consultation between customers and acall center (e.g., explanation of how to use home
appliances and solve problems)• Remote monitoring to understand the situation at
another place of business from the office or tocheck on conditions at home while away on business• Broadcasting to the home or office the conditionsat an exhibition or during a trip• Distance learning while at home or traveling
The fusion of the Internet and cellular phones isexpected to increase the opportunities for video communication.
5. Future development
We will continue to improve the functions of PCC
and add new functions in response to customer needs
and utilize NTT research results as well as technology on the market to increase the added value.
References
[1]
[2]

[3]

http://www.dpbv-service.com/ (in Japanese).
H. Takeda, M. Moriuchi, T. Imaeda, S. Honda, and T. Yasuno,“Videoconferencing Technology for High-quality PC MultipointConnections,” NTT Technical Review, Vol. 3, No. 10, pp. 25-30,2005.
Y. Yamanaka, S. Esaki, A. Shibata, S. Takada, and S. Seto, “NetworkTechnology to Support PC Communication Services,” NTT Technical Review, Vol. 3, No. 10, pp. 31-35, 2005.

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Special Feature

Hideaki Takeda

Shigehiko Onishi

Senior Research Engineer, Supervisor, Promotion Project 1, NTT Cyber Solutions Laboratories.
He received the B.E. and M.E. degrees in electrical engineering from Hokkaido University,Sapporo, Hokkaido in 1979 and 1981, respectively. In 1983, he joined the Electrical Communication Laboratories of Nippon Telegraph andTelephone Public Corporation (now NTT),
Kanagawa. He has been engaged in R&D ofinformation systems. He is a member of theInformation Processing Society of Japan.

Manager, Visual Communications Division,NTT IT Corp.
He received the B.E. and M.E. degrees in electrical & computer engineering from Yokohama
National University, Yokohama, Kanagawa, in1989 and 1991, respectively. He joined NTT LSILaboratories in 1991. From 2000 to 2003, he waswith ATR Spoken Language Translation
Research Laboratories, Kyoto, Japan. From 2003
to 2005, he was engaged in research on videocoding systems at NTT Cyber Space Laboratories. His research interests include audio/speech
signal processing and image processing. He is amember of IEICE and ASJ.

Dai AndoHirohisa Jozawa

Research Engineer, Promotion Project 1, NTT
Cyber Solutions Laboratories.
He received the B.E. degree in information
technology from Tohoku University, Sendai,
Miyagi in 1989. In 1989, he joined NTT Human
Interface Laboratories and has mainly been
engaged in developing video communication
systems. He is a member of the Institute of Electronics, Information and Communication Engineers (IEICE) of Japan.

Senior Manager, NTT Resonant Inc.
He received the B.E. and M.E. degrees in electrical engineering from Waseda University,Tokyo, in 1987 and 1989, respectively. He joined
NTT Human Interface Laboratories in 1989 andwas engaged in R&D of video coding systems.
He was a Senior Research Engineer, Supervisorof NTT Cyber Space Laboratories, and moved toNTT Resonant Inc. in 2004. He is a member ofIEICE and the Institute of Image Information andTelevision Engineers of Japan.

Sumitaka Sakauchi
Associate Manager, NTT Advanced Technology Corporation.
He received the B.S. degree in physics fromYamagata University, Yamagata in 1993, theM.S. degree in physics from Tohoku University,Sendai, Miyagi in 1995, and the Ph.D. degree inengineering from Tsukuba University, Tsukuba,Ibaraki in 2005. He joined NTT in 1995. Until
2005, he was engaged in R&D of acoustic echo
cancellation and noise reduction as a ResearchEngineer, Media Processing Project, NTT CyberSpace Laboratories. He moved to the present
position in 2005. He received the Best Paper
Award from IEICE in 2001. He is a member ofthe Acoustical Society of Japan (ASJ) andIEICE.

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