Uplink Power Control for Power Limited Terminals

TECHNICAL FIELD [0001] The present invention relates generally to wireless communication systems, and more particularly to methods, devices and systems for managing transmit power in a wireless communication system.

BACKGROUND OF THE INVENTION [0002] Radio access technologies for mobile mobile networks are constantly evolving to meet the demand for higher data rates, increased coverage and increased capacity. An example of the recent development of broadband code access technology in the field of code (WCDMA, Wideband Code-Division Muitiple Access) is the so-called HSPA (High-Speed ​​Packet Access) technology developed by the 3rd-Generation Partnership Project (3GPP). Further development of 3G systems takes place in the LTE (Long Term Evolution) initiative 3GPP, which includes the development and specification of new access technologies and new system architectures. A review of LTE systems is presented in the document "Evolved Universa! Terrestrial Radio Access (E-UTRA) and Evoived Universai Terrestrial Radio Access NetWork (EUTRAN); Overa! L Description, Stage 2,

One of the objectives of the LTE initiative is that access technology should provide flexibility to be applicable to known frequency allocations, as well as for new frequency allocations. This solution allows easy entry into the spectrum with the existing use. For similar reasons, LTE is designed to be used with a number of duplex solutions. Both frequency duplex duplex (FDD) and time division duplex (TDD) are supported, in which both uplink and downlink transmissions are distributed, respectively, frequency and time to allow the use of LTE technology with paired and unpaired spectrum allocations. In addition, to allow even greater flexibility in the use of available spectrum, LTE access technology is based on multi-access OFDMA (Orthogonai Frequency Division MUIPIPLE Access) for downlink and SC-FDMA (Single-Carrier Frequency Division MULLIPLE Access) for uplink. These technologies enable an accurate, dynamic allocation of spectral resources for uplink and downlink communication. Thus, available resources can be adjusted dynamically based on individual user requirements as well as aggregated demand.

[0004] In general, in wireless communication systems, transmission with excessive power levels should be avoided (e.g., power levels greater than necessary to maintain the desired quality of service). This is generally desirable to avoid interference with other transmitted signals and is particularly desirable in mobile terminals for maximizing the time between terminal battery charging. Therefore, the LTE specifications support a power control mechanism in which the serving base station (in 3GPP terms evolved node Node-B or eNodeB) regulates the output power of the mobile terminal transmitter, [0005] A basic overview of the power regulation mechanism for LTE is provided in the document "Evo! Ved Universal

-2Terrestrial Radio Access (E-UTRA); Physical layer procedures ", 3GPP TS 36.213, v. 8.1.0, dated December 12, 2007. The defined mechanism ensures that the power setting for each transmission of the sub-frame of the mobile terminal is calculated as a function of bandwidth allocated for subframe, modulation scheme and coding allocated for subframe and current estimation of propagation losses. In some operating modes, the output power of the transmitter is further calculated as a function of a parameter representing the accumulated transmit power control (TPC) commands received by the mobile terminal.

[0006] This initial power regulation mechanism specified by 3GPP is provided in connection with the support for dynamic scheduling allowed in the LTE system. The bandwidth and modulation scheme used by the mobile terminal may vary for each subframe - to avoid transmitting with excessive power levels, the transmit power level of the transmitter must vary with these changes in resource allocation. The output power level of the transmitter is also dynamically adjusted to adapt to propagation changes, e.g. transmission losses. However, the power control mechanism described in the above-mentioned 3GPP specification does not adequately support power limiting cases.

[0007] A probe with a power transmission control mechanism in power limiting situations is noted in other wireless communication systems. For example, the document US Patent Publication No. 2006/0050798, by Odigie et al., Dated 9 March 2006, describes the operation of the transmit power control system in the power limiting circumstances of WCDMA (Wideband Code-Division Muitiple Access). However, the methods and device disclosed by Odigie do not relate to the dynamic scheduling of resources acceptable in LTE systems. In addition, the systems disclosed by Odigie do not use the accumulated TPC command parameter according to the LTE specification.

SUMMARY OF THE INVENTION [0008] The present invention provides a method and a mobile terminal for efficiently adjusting the uplink transmit power of an mobile terminal in LTE and other systems using closed-loop power control, respectively, according to claim 1. 1 and 11. In some embodiments, the mobile terminal is adapted to effectively ignore the transmit power control commands "UP" in the case where the mobile terminal is operating in a power limited state.

[0009] In an exemplary method of controlling transmit power in a mobile terminal, a number of transmit power control commands are received, wherein each transmit power adjustment command indicates a change in transmit power relative to the previous transmission over this mobile terminal. The accumulated power control value is changed in response to any transmit power control command which indicates a negative transmit power change, i.e. each power control command "W DOWN" ("DOWN"). However, this accumulated power control value is changed in response to the power control command "UP", i.e. the transmit power control command, which indicates a positive change in transmit power only when the mobile terminal is not in the power limiting state. So, in some examples, this accumulated power control value is changed to higher only if the transient power setting is less than the transmit power limit for the mobile terminal. This transient power setting is output from the accumulated power control value and one or more radio link parameters. The method further comprises calculating transmit power settings for each transmission by the mobile terminal, based on the accumulated power control value and one or more radio link parameters.

[0010] Ignoring the power control commands "UP", being in the power limiting state, the mobile terminal avoids accumulation of power control changes that are produced by the serving base station when the mobile terminal has a power limitation. This solution allows faster convergence to the optimal transmit power setting when the mobile terminal is in a power limiting state.

[0011] In one or more embodiments of the invention, the transient power settings and transmit power settings are determined based on the accumulated power control value and radio link parameters, which may include one or more of the transmission bandwidth, estimates of transmission propagation losses and modulation coding scheme. In some examples, the transient power setting and transmission power setpoints may further be determined as a function of one or more offset values ​​provided by the serving base station. These offset values ​​may be one or both of the transmit power shift dependent on the cell and the shifting of the transmit power depending on the mobile terminal. In still other examples, the status of the mobile terminal is monitored for one or more predetermined criteria for restoring the initial transmit power adjustment; in response to each such occurrence, the accumulated power control value is reset to a predetermined value.

[0012] Also disclosed are mobile terminals adapted to perform one or more of the power control methods described herein.

BRIEF DESCRIPTION OF THE DRAWINGS [0013]

Fig. 1 illustrates the band allocation between a number of users in the LTE system.

Fig. 2 shows a wireless system comprising a mobile terminal according to one or more embodiments of the present invention.

Fig. 3 is a block diagram illustrating an exemplary method of controlling transmit power in a mobile terminal in a wireless communication system.

Fig. 4 is a block diagram illustrating an exemplary method for monitoring the renewal criteria for transmit power control.

DETAILED DESCRIPTION [0014] In the following description, various aspects of the present invention have been described with reference to the LTE standard in the 3GPP development. Qualified people will recognize that these techniques can be used for other wireless systems using power control. Similarly, the methods and apparatus may be described below with respect to an LTE mobile terminal; skilled persons will appreciate that the techniques described herein can be easily adapted for mobile terminals adapted for use in one or more other wireless communication systems. Finally, those skilled in the art will recognize that the term "mobile terminal" as used herein is intended to encompass each of a wide variety of end-user devices, including in particular each of those devices referred to as "user equipment" ("UE", "User Equipment") or "mobile station" by various specifications promulgated by the organization 3rd-Generation Partnership or other groups of standards. Furthermore, the term "mobile station" includes wireless terminals adapted for M2M (machine-to-machine) applications as well as wireless terminals adapted for stationary wireless communication.

- that the mobile terminals discussed herein may be mobile radios adapted for voice communication, data communication or both; PDA (personal digttal assistant) devices adapted for wireless communication; conventional laptop computers and / or palmtops or other devices that include a wireless transceiver system; as well as cards and modules for wireless transceiver systems adapted for use in computer devices that may or may not be portable. Thus, the following description and attached drawing should be seen as an illustration of the present invention and not a limitation thereof.

[0015] The LTE specification supports fast link scheduling and adaptation, in the fields of frequency and time, for both uplink and downlink communication. This means that resource assignments in time and frequency can be adjusted according to the momentary traffic demand of each user and changes in the channel. In an upstream LTE connection, it is possible to simultaneously arrange a number of users (i.e. in the same subframe) by allocating different frequency segments to different users. However, for the preservation of a single-carrier structure with SC-FDMA, each user can only receive a continuous allocation in frequency. In other words, although a variable number of resource blocks may be allocated to the user (the LTE resource block is defined as 12 neighboring subcarriers, each of 15 kHz wide, for a subframe with a duration of 1 millisecond), these resource blocks must be adjacent. Fig. 1 illustrates an exemplary allocation of frequency transmit resources for three users, where User 1 is allocated a much larger block of frequency resources than User 2 and User 3. These frequency assignments may vary between subframes, thus e.g. User 1 in a subsequent subframe is allocated a smaller the number of resource blocks or no resource blocks assigned to it at all.

[0016] Fig. 2 is a simplified view of a wireless communication system including an exemplary mobile terminal 200 configured in accordance with one or more embodiments of the present invention and a base station 250. The mobile terminal 200 includes a radio transceiver module 210, which in certain embodiments can be configured according to the LTE specification. In this case, the serving base station 250 may be an evolved Node B or eNodeB node configured according to the LTE specification. The radio transceiver module 210 may also be compatible with one or more additional wireless communication standards, including the standards of wide area wireless networks, e.g. broadband CDMA or GSM, or local wireless network standards, e.g. one or more standards from the IEEE 802.11 family. The mobile terminal 200 further includes a controller 220; the controller 220 functions may include the processing of the scheduling allocation information and the transmit power control (TPC) commands received from the base station, as well as determination of the output power settings for transmission by the transceiver module 210 to the base station 250. In particular, as will be described in more detail below, the controller 220 may in certain embodiments be adapted to change the accumulated power control value in response to each TPC command that indicates a negative transmit power change, i.e. a TPC command "DOWN", but to changes in the accumulated power control value in response to each TPC command,

The accumulated power control value indicates that the mobile terminal has no power limitation. The controller 220 is further configured to output the transmit power setting for each transmission through the radio transceiver module 210 based on the accumulated power control value and one or more radio link parameters. The mobile terminal 200 also includes a memory 230 that may include software. and data for adapting the controller 220 according to one or more embodiments of the present invention. The memory 230 may also store one or more radio link parameters used by the controller 220 to determine the output power settings - some of these power control parameters may be statically configured, i.e. stored in the memory 230 during production, others may be configured semistatically, i.e. configured by signaling information received from the base station 250. The memory 230 may further be used to store the accumulated power control value according to one or more embodiments of the invention. The memory 230 may include one or more storage devices, including, but not limited to, flash memory, ROM, RAM (e.g., SRAM and / or DRAM), one or more disk drives, or other volatile or non-volatile memory devices.

[0018] As indicated above, the basic power control mechanism for LTE is defined in the document "Evolved Universal Terrestrial Radio Access (E-UTRA); Physical layer procedures ", 3GPP TS 36.213, v. 8.1.0, dated December 12, 2007. The defined power control procedure ensures that the power setting for each transmission of the sub-frame of the mobile terminal is determined as a function of the bandwidth allocated for this subframe, modulation and scheme coding allocated for this subframe and current estimation of propagation losses. In some operating modes, the transmitter's output power is further determined as a function of the parameter representing the accumulated transmit power control (TPC) commands received by the mobile terminal. If the determined transmitter output setting exceeds the maximum output power for the mobile terminal, then this mobile terminal transmits at this maximum level. Thus, the transmit power setting for transmission in a physical uplink shared channel (PUSCH) is determined as:

P_T(j) = min {P_liŁV?10dog (5fn /]) +]) + α-PL + P_OFPSEr + TPC_{aceill) t}and TPCacam is the accumulated power control value representing the accumulation of transmit power commands received from the serving eNodeB node. A similar pattern is used to determine the transmit power setting for transmission via a physical uplink control channel (PUCCH).

[0019] The accumulated power control value TPCaccum is updated in time based on newly received TPC commands. These TPC commands are received by the downlink control channel in one of at least two formats. In the first format, the TPC command is received in the scheduling grant from the eNodeB node. In this format, the TPC command can take values ​​[-1,0,1,3] dB or [-1,1,1,3] dB, depending on the parameters of the semistatic configuration determined by signaling the upper layer. In the second format, the TPC command for the mobile terminal is encoded together with other transmit power control commands in the downlink control channel and can take values ​​according to one of the following sets, again according to the semistatic configuration parameters determined by higher layer signaling: [-1,1 ] dB, [-1, 0,1,3] dB or [-3, -1.31,3] dB. The accumulated value of the power regulation for the given subframe / is given by the expression:

<a name="caption1"></a>/ (0 = / 0-1) + Δ ^ (/ ~ 4), (2) where f {0) = 0, and Arpc (/ - 4) represents the value of the TPC command received four subframes earlier.

[0020] As can be seen in equation (1), a mobile transmitter may have a power limitation in a given subframe. According to equation (1), if the power set-point derived for bandwidth, modulation coding scheme etc. exceeds the maximum power allowed for this mobile terminal, then the maximum power level of the terminal is used. However, the above-defined accumulation of TPC commands does not provide an exception for cases with power limitations. As a result, power control commands are accumulated even when the mobile terminal has a power limitation.

[0021] For example, when the mobile terminal is allocated a wide band, i.e. when BW [z] in the above formulation is large, and / or when the propagation losses PL are large, the power control component 10 log (BW [/]) + AMcs ( MCS [ij] + α PL + Poffset + TPCaccum could be larger than the maximum transmit power. Thus, the mobile terminal has a power limitation. The eNodeB may state that the mobile terminal has not reached the signal-to-noise ratio (SNR) or signal-to-interference-plus ratio (SINR). noise ratio), and therefore instruct this mobile terminal to increase power by sending TCP commands "UP", i.e. Atpc (/ - 4)&gt; 0. If the power limitation situation lasts for a long time, the accumulated power control value can continue to increase without restrictions . As long as the mobile terminal is scheduled to transmit with a wide band or until propagation losses remain high, the mobile terminal may indeed need a maximum transmit power level. (In some cases, the transmit power can not be limited to such an extent that the eNodeB can not completely receive the transmission of the mobile terminal). However, if the scheduler changes the bandwidth allocation into a smaller band or if the radio propagation conditions change significantly, then the maximum power of the mobile terminal could be too high and the SINR value for the reception will exceed the target value. Although the open loop component of the power control pattern will match the new band allocation through the 10 · logw {6W [/] component. the accumulated commands "UP" in the closed loop component (eg TPCaccum) may be a problem. If the accumulated TPCaccum power control value is large, the portable terminal will continue to transmit at maximum power until the accumulated power control value is reduced by subsequent TPC commands "DOWN". This may require a number of subframes; at this time, the mobile terminal will transmit unnecessarily high power levels, causing interference for

- 7 signal transmitters of other mobile terminals and unnecessarily exhausting the battery of this mobile terminal.

[0022] One approach to solving this problem would be to modify the eNodeB node processes for power control. For example, the eNodeB node could be adapted to stop sending commands "UP", if the ratio SINR does not increase in response to previous commands "UP". Alternatively, the eNodeB could be adapted to avoid sending commands "UP" when the bandwidth allocation is wide. However, probably none of these solutions results in optimal performance because the target SINR value changes as a result of interference changes and frequency selectivity of the channel. This is particularly the case for the allocation of narrow bandwidth. Alternatively, the eNodeB could require the mobile terminal to frequently send power reports so that the eNodeB can determine whether the mobile terminal has a power limitation or not. However, this solution causes a significant up-stream signaling overhead. An improved solution according to one or more embodiments of the present invention is a modification of the power control procedures previously specified by the LTE initiative for the mobile terminal. In this modified procedure, for modes of operation in which the transmit power setting is based on an accumulated control value At first, the transient power setting is calculated using the basic formulation of equation (1). This transient power set-up is calculated based on the current values ​​for each of a number of radio link parameters. In contrast, this transient power setting is calculated based on the previous value of the accumulated power control value. Therefore:

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[0024] The update of the accumulated power control value TPCaccum (i -1) is based on the calculated transient power setting. Briefly, positive TPC commands, ie "UPDATES" are not accumulated if the mobile terminal is already limited to its maximum output power, i.e. if Pprov&gt; Ρμαχ, then TPCaccumij) = TPCaecum (i - 1) + min { 0, Atpc (/ - 4)} Otherwise, the accumulated power control value is updated with each received TPC command. Ie, if Pprov ά Ρμαχ, then TPCaccumlfi = TPCaccum (i - 1) + &amp; TPC (j - 4) .

[0025] The above power regeneration procedure is directly applicable to determining transmit power settings for transmission over LTE mobile terminals, e.g., mobile terminal 200, via a physical uplink shared channel (PUSCH). Of course, similar modifications can be made to determine transmit power settings for transmission via the physical uplink control channel (PUCCH) of the LTE. Of course, skilled persons will recognize that the techniques described herein can be applied to other wireless systems and can be modified in various ways. Thus, a more general outline of the method of controlling transmit power in a mobile terminal in a wireless communication system is provided in the block diagram of Fig. 3.

Each iteration of the logic flow of Fig. 3 begins with the reception of the transmit power control command (TPC) from the serving base station, as shown in block 310. In the LTE system described above, the TPC command may take any one of a number of values, depending on from the current configuration of the mobile terminal. On some systems, the TPC commands can be limited to the commands "UP" and "DOWN", where "UP" and "DOWN" indicate the set incremental adjustment, eg by 1 dB, relative to the previous power

-8nadawczej. In others, TPC commands can take values ​​from a wider range. Those skilled in the art will also recognize that in some systems there may be a slight delay between the actual reception of the TPC command and its use to calculate transmit power settings. For example, in the procedures discussed above for LTE discussed above, the output of the transmit power set for the subframe / is based on the TPC command obtained in the subframe and - 4. In other systems, the delay may be longer or shorter than this.

[0027] As discussed above with respect to LTE, TPC commands may be received from a serving base station via a control channel. In some embodiments of the invention, TPC commands may be sent according to the allocation format format or power control command format, so in certain example embodiments of the present invention it may be required to acquire transmit power control commands from a control channel compatible with one of these formats or with both of them .

[0028] In any case, if the TPC command indicates a downward adjustment, i.e. if the change from the previous transmit power is negative, which is found in block 320, then the processing continues in block 350, where the accumulated power control value is changed according to this TPC command. In block 360, the transmit power setting is then determined for the current transmission based on the accumulated power control value and one or more radio link parameters. For LTE, these radio link parameters include allocated transmission bandwidth, modulation / coding scheme parameters, and estimation of propagation losses. In other systems, radio link parameters may include one or more of these radio link parameters and / or one or more other radio link parameters. In some instances, the biasing 360 of the transmit power setting may also be based on one or more offset values. These offset values ​​may include a cell-dependent shifting of the transmit power or a shift of transmission power dependent on the mobile terminal, or both. One or more of these offset values ​​can be received from the serving base station. These offset values ​​may include a cell-dependent shifting of the transmit power or a shift of transmission power dependent on the mobile terminal, or both. One or more of these offset values ​​can be received from the serving base station. These offset values ​​may include a cell-dependent shifting of the transmit power or a shift of transmission power dependent on the mobile terminal, or both. One or more of these offset values ​​can be received from the serving base station.

[0029] Skilled persons will recognize that the 360 ​​transmit power setting in the bias may, in certain circumstances, reflect a power limitation situation even if the accumulated power control value has been changed downwards. However, every downward change in the accumulated power control value makes the mobile terminal somewhat "less" limited in terms of power than would otherwise be the case. After a number of such changes to the accumulated power control value, the mobile terminal may exit the power limiting state, so that the TPC commands will actually adjust the transmit power down.

[0030] On the other hand, if the received TPC command indicates an upward adjustment with respect to the previous transmit power, which again is found in block 320, a transient power setting is output at block 330. This transient power set-up is calculated on the basis of the same one or more of the radio link parameters discussed above, but is based on the previous setting of the accumulated TPC value, e.g. directly from the previous value. Thus, outputting this transient power setting reflects the transmit power setting assuming that the accumulated TPC value is not up-regulated according to the current TPC command. Of course, this transient power setting is not necessarily calculated "from zero" - in some cases, this transient power setting can be calculated simply

By adjusting the previous transient power setting for any changes in radio link parameters. [0031] At block 340, the mobile terminal determines whether there is a power limitation based on the transient power setting. In some examples, it is stated that the mobile terminal has a power limitation, if this transient power setting is greater than the power limit for this mobile terminal. In others, the mobile terminal is considered to have a power limitation if this transient power setting is greater than or equal to the power limit of the mobile termina. In any case, if the mobile terminal has a power limitation, then the accumulated power control value is not changed, and the processing goes to block 360, in which the transmit power setting is output. Of course, in this case,

[0032] On the other hand, if the transient power setting is less than the power limit of the mobile terminal, then the accumulated power control value is changed in block 350 to reflect the received TPC command "UP". The transmit power setting is calculated in block 360; this transmit power setting in this case reflects the current radio link parameters and the updated accumulated power control value.

[0033] In the method shown in Fig. 3, it is implicitly assumed that there exists a previous accumulated power control value; i.e. that the previous value of the accumulated power control value can be updated based on the received TPC command. In the LTE specification referenced earlier, the accumulated value of the power control commands is preset to zero; however, no criteria have been defined for restoring the initial accumulated power control value. In practice, various criteria may be needed to restore the initial accumulated power control value. For example, as will be appreciated by skilled persons, different cells may have different mismatches of the up / down link propagation mismatch, due to power line losses and other aspects related to the system implementation. When the mobile terminal enters a new cell, any cell-dependent offset values ​​used to calculate the transmit power settings may be updated to reflect the new cell configuration. This can happen, for example, by receiving new cell-dependent values ​​of shifts sent to the mobile station via the control channel. These new cell-dependent offset values ​​can then be used by the mobile terminal for subsequent calculations of the power setting. However, if the accumulated power control values ​​would not be restored to the initial value in such a situation, adjusting the transmit power settings to the appropriate level could be unnecessarily delayed. Indeed, because TPC commands in LTE are usually only sent when the mobin terminal has data for transmission, and not in advance, this may result in unnecessary HARQ (automatic automatic repeat request) and HARQ failures. Furthermore, if the new cell does not know the TPC commands sifted from the first cell, the new eNodeB can not track the transmit power of the mobile terminal. There may be other situations in which restoring the initial accumulated TPC values ​​is advantageous, e.g. when the UE attempts to synchronize the uplink after losing the uplink synchronization.

[0034] Accordingly, in certain example embodiments of the present invention, the mobile terminal is provided with criteria for when to start a new accumulation of the TPC. For example, the LTE mobin terminal may be

Adapted using the criteria for restoring the initial value of the TPC accumulation corresponding to uplink transmissions on a shared uplink channel (PUSCH). In some examples, the same criteria may be used to restore the initial value of a separate accumulation of TCP tensions for an uplink control channel (PUCCH). In others, separate criteria may be provided for restoring the initial accumulated TCP value for the PUCCH.

[0035] Examples of such criteria include, but are not limited to: detection of a change in a serving cell; an attempt to obtain an uplink synchronization after losing synchronization; long periods of discontinuous DRX reception - e.g. when the time from transmission in the PUSCH or PUCCH channel exceeds the designated threshold value; entering or leaving an active state; receiving a TPC command indicating that an absolute power shift should be used to calculate the transmit power setting instead of the accumulated power control value; and changing one or more power control parameters regulated by the system, e.g. a propagation loss factor a or a Poffset offset parameter from equation (1). Skilled people will notice

[0036] Fig. 4 therefore illustrates a method of evaluating whether an accumulated power control value should be restored to an initial value. In some embodiments of the invention, the accumulated power control value is restored to zero, although other initial values ​​are possible. Those skilled in the art will recognize that the method illustrated in Fig. 4, or variants thereof, may be combined in certain embodiments of the invention with the method illustrated in Fig. 3.

[0037] In any case, each iteration of the method illustrated in Fig. 4 begins with an evaluation of whether the serving cell has changed as shown in block 410. (Of course, the illustrated ratings in blocks 410-460 can be carried out in the correct order.) If yes, control goes to block 470, where the initial accumulated power control value is restored. If not, then additional criteria for the restoration of the initial accumulated power control value are evaluated in a similar manner. Thus, in block 420, the mobile station determines whether uplink synchronization has been lost in block 430, whether the time since the last transmission exceeds a predetermined threshold, and in block 440 whether a new power control parameter has been received from the serving base station. Similarly, in block 450, the mobile station assesses whether she came out of active state or entered it, and in block 460, whether she received from the base station the command of absolute shifting of power. If any of these initial value restoration criteria are met, block 470 restores the initial accumulated power control value. Otherwise, these criteria are re-evaluated.

[0038] The various methods described above, as well as variants thereof, may be implemented in mobile terminals, e.g. mobile terminals 200 shown in Fig. 2, adapted to operate in a wireless communication system using closed-loop control. Of course, the present invention may be implemented in other ways than specifically illustrated herein, without departing from the essential characteristics of the present invention as defined by the appended claims.